diff --git a/ext/ldap/tests/skipifbindfailure.inc b/ext/ldap/tests/skipifbindfailure.inc
index 81c7998cfbb5..feb8faefbf3d 100644
--- a/ext/ldap/tests/skipifbindfailure.inc
+++ b/ext/ldap/tests/skipifbindfailure.inc
@@ -1,14 +1,24 @@
 <?php
 require_once 'connect.inc';
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
 
 if ($skip_on_bind_failure) {
+    $configuration = [$uri, $user, $passwd, $protocol_version];
 
-    $link = ldap_connect($uri);
-    ldap_set_option($link, LDAP_OPT_PROTOCOL_VERSION, $protocol_version);
-    if (!@ldap_bind($link, $user, $passwd))
-        die(sprintf("skip Can't bind to LDAP Server - [%d] %s", ldap_errno($link), ldap_error($link)));
+    $reason = ProbeCache::getFailure('ldap.bind', $configuration, static function () use ($uri, $user, $passwd, $protocol_version): ?string {
+        $link = ldap_connect($uri);
+        ldap_set_option($link, LDAP_OPT_PROTOCOL_VERSION, $protocol_version);
+        if (!@ldap_bind($link, $user, $passwd)) {
+            return sprintf("Can't bind to LDAP Server - [%d] %s", ldap_errno($link), ldap_error($link));
+        }
+
+        ldap_unbind($link);
+        return null;
+    });
 
-    ldap_unbind($link);
+    if (is_string($reason)) {
+        die("skip $reason");
+    }
 }
 
 if (isset($require_vendor)) {
diff --git a/ext/mysqli/tests/skipifconnectfailure.inc b/ext/mysqli/tests/skipifconnectfailure.inc
index 986f646f8bb9..eb7dee5f60bf 100644
--- a/ext/mysqli/tests/skipifconnectfailure.inc
+++ b/ext/mysqli/tests/skipifconnectfailure.inc
@@ -1,7 +1,20 @@
 <?php
 require_once 'connect.inc';
-$link = @my_mysqli_connect($host, $user, $passwd, $db, $port, $socket);
-if (!is_object($link))
-    die(sprintf("skip Can't connect to MySQL Server - [%d] %s", mysqli_connect_errno(), mysqli_connect_error()));
-mysqli_close($link);
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
+
+$configuration = [$host, $port, $user, $passwd, $db, $socket, get_environment_connection_flags()];
+
+$reason = ProbeCache::getFailure('mysqli', $configuration, static function () use ($host, $user, $passwd, $db, $port, $socket): ?string {
+    $link = @my_mysqli_connect($host, $user, $passwd, $db, $port, $socket);
+    if (!is_object($link)) {
+        return sprintf("Can't connect to MySQL Server - [%d] %s", mysqli_connect_errno(), mysqli_connect_error());
+    }
+
+    mysqli_close($link);
+    return null;
+});
+
+if (is_string($reason)) {
+    die("skip $reason");
+}
 ?>
diff --git a/ext/mysqli/tests/test_setup/test_helpers.inc b/ext/mysqli/tests/test_setup/test_helpers.inc
index c9ab401e7568..e980044e635d 100644
--- a/ext/mysqli/tests/test_setup/test_helpers.inc
+++ b/ext/mysqli/tests/test_setup/test_helpers.inc
@@ -1,5 +1,7 @@
 <?php
 
+require_once dirname(__DIR__, 4) . '/tests/probe_cache.inc';
+
 function get_default_host(): string {
     static $host = null;
     if ($host === null) {
@@ -110,12 +112,33 @@ function default_mysqli_connect(): \mysqli{
 function mysqli_check_skip_test(): void {
     mysqli_connect_or_skip();
 }
-function mysqli_connect_or_skip() {
-    try {
-        return default_mysqli_connect();
-    } catch (\mysqli_sql_exception) {
-        die(sprintf("skip Can't connect to MySQL Server - [%d] %s", mysqli_connect_errno(), mysqli_connect_error()));
+
+function mysqli_connect_or_skip(): mysqli {
+    $connection = null;
+    $configuration = [
+        get_default_host(),
+        get_default_port(),
+        get_default_user(),
+        get_default_password(),
+        get_default_database(),
+        get_default_socket(),
+        get_environment_connection_flags(),
+    ];
+
+    $reason = ProbeCache::getFailure('mysqli', $configuration, static function () use (&$connection): ?string {
+        try {
+            $connection = default_mysqli_connect();
+            return null;
+        } catch (mysqli_sql_exception $e) {
+            return sprintf("Can't connect to MySQL Server - [%d] %s", mysqli_connect_errno(), mysqli_connect_error());
+        }
+    });
+
+    if (is_string($reason)) {
+        die("skip $reason");
     }
+
+    return $connection;
 }
 function have_innodb(mysqli $link): bool {
     $res = $link->query("SELECT SUPPORT FROM INFORMATION_SCHEMA.ENGINES WHERE ENGINE = 'InnoDB'");
@@ -123,11 +146,7 @@ function have_innodb(mysqli $link): bool {
     return $supported === 'YES' || $supported === 'DEFAULT';
 }
 function mysqli_check_innodb_support_skip_test(): void {
-    try {
-        $link = default_mysqli_connect();
-    } catch (\mysqli_sql_exception) {
-        die(sprintf("skip Can't connect to MySQL Server - [%d] %s", mysqli_connect_errno(), mysqli_connect_error()));
-    }
+    $link = mysqli_connect_or_skip();
     if (! have_innodb($link)) {
         die(sprintf("skip Needs InnoDB support"));
     }
diff --git a/ext/odbc/tests/skipif.inc b/ext/odbc/tests/skipif.inc
index 9785f5843a77..be05da96f0a2 100644
--- a/ext/odbc/tests/skipif.inc
+++ b/ext/odbc/tests/skipif.inc
@@ -1,8 +1,18 @@
 <?php
 
 include 'config.inc';
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
 
-$conn = @odbc_connect($dsn, $user, $pass);
-if (!$conn) {
-    die('skip could not connect');
+$conn = null;
+$reason = ProbeCache::getFailure('odbc', [$dsn, $user, $pass], static function () use ($dsn, $user, $pass, &$conn): ?string {
+    $conn = @odbc_connect($dsn, $user, $pass);
+    if (!$conn) {
+        return 'could not connect';
+    }
+
+    return null;
+});
+
+if (is_string($reason)) {
+    die("skip $reason");
 }
diff --git a/ext/pdo/tests/pdo_test.inc b/ext/pdo/tests/pdo_test.inc
index b44d0b88e77b..2776c9811ec3 100644
--- a/ext/pdo/tests/pdo_test.inc
+++ b/ext/pdo/tests/pdo_test.inc
@@ -1,6 +1,8 @@
 <?php
 # PDO test framework utilities
 
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
+
 if (getenv('PDOTEST_DSN') === false) {
     $common = '';
     $append = false;
@@ -18,41 +20,51 @@ if (getenv('PDOTEST_DSN') === false) {
 class PDOTest {
     // create an instance of the PDO driver, based on
     // the current environment
-    static function factory($classname = PDO::class, bool $useConnectMethod = false) {
+    static function factory($classname = PDO::class, bool $useConnectMethod = false, ?array $attributes = null) {
         $dsn = getenv('PDOTEST_DSN');
         $user = getenv('PDOTEST_USER');
         $pass = getenv('PDOTEST_PASS');
-        $attr = getenv('PDOTEST_ATTR');
-        if (is_string($attr) && strlen($attr)) {
-            $attr = unserialize($attr);
-        } else {
-            $attr = null;
+        if ($attributes === null) {
+            $attributes = self::getAttributes('PDOTEST_ATTR');
+            if (getenv('TEST_PHP_EVALUATING_SKIPIF') === '1') {
+                $skipAttributes = self::getAttributes('PDOTEST_SKIP_ATTR');
+                if ($skipAttributes !== null) {
+                    $attributes = $skipAttributes + ($attributes ?? []);
+                }
+            }
         }
 
         if ($user === false) $user = NULL;
         if ($pass === false) $pass = NULL;
 
-        if ($useConnectMethod) {
-            $db = $classname::connect($dsn, $user, $pass, $attr);
-        } else {
-            $db = new $classname($dsn, $user, $pass, $attr);
+        if (getenv('TEST_PHP_EVALUATING_SKIPIF') !== '1') {
+            return self::createConnection($classname, $useConnectMethod, $dsn, $user, $pass, $attributes);
         }
 
-        if (!$db) {
-            die("Could not create PDO object (DSN=$dsn, user=$user)\n");
+        $database = null;
+        $exception = null;
+        $configuration = [$classname, $useConnectMethod, $dsn, $user, $pass, $attributes];
+
+        $reason = ProbeCache::getFailure('pdo', $configuration, static function () use (&$database, &$exception, $classname, $useConnectMethod, $dsn, $user, $pass, $attributes): ?string {
+            try {
+                $database = self::createConnection($classname, $useConnectMethod, $dsn, $user, $pass, $attributes);
+                return null;
+            } catch (PDOException $e) {
+                $exception = $e;
+                return $e->getMessage();
+            }
+        });
+
+        if (is_string($reason)) {
+            throw $exception ?? new PDOException($reason);
         }
-        // Ignore errors about non-existent tables
-        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);
 
-        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
-        $db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
-        $db->setAttribute(PDO::ATTR_STRINGIFY_FETCHES, true);
-        return $db;
+        return $database;
     }
 
     static function skip() {
         try {
-            $db = PDOTest::factory();
+            self::factory();
         } catch (PDOException $e) {
             die("skip " . $e->getMessage());
         }
@@ -95,6 +107,33 @@ class PDOTest {
             default => $db->exec("DROP TABLE IF EXISTS $tableName"),
         };
     }
+
+    private static function createConnection($classname, bool $useConnectMethod, $dsn, $user, $pass, ?array $attributes) {
+        if ($useConnectMethod) {
+            $db = $classname::connect($dsn, $user, $pass, $attributes);
+        } else {
+            $db = new $classname($dsn, $user, $pass, $attributes);
+        }
+
+        if (!$db) {
+            die("Could not create PDO object (DSN=$dsn, user=$user)\n");
+        }
+        // Ignore errors about non-existent tables
+        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT);
+
+        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
+        $db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
+        $db->setAttribute(PDO::ATTR_STRINGIFY_FETCHES, true);
+        return $db;
+    }
+
+    private static function getAttributes(string $environmentVariable): ?array {
+        $attributes = getenv($environmentVariable);
+        if (is_string($attributes) && strlen($attributes)) {
+            return unserialize($attributes);
+        }
+        return null;
+    }
 }
 /** See https://stackoverflow.com/a/3732466 */
 function get_dummy_sql_request(): string
diff --git a/ext/pdo_dblib/tests/common.phpt b/ext/pdo_dblib/tests/common.phpt
index 293597b623e3..f3a963ef9b63 100644
--- a/ext/pdo_dblib/tests/common.phpt
+++ b/ext/pdo_dblib/tests/common.phpt
@@ -5,7 +5,7 @@ pdo_dblib
 --REDIRECTTEST--
 # magic auto-configuration
 
-return [
+$config = [
 	'ENV' => [
 		'PDOTEST_DSN'  => getenv('PDO_DBLIB_TEST_DSN')  ?: 'dblib:host=localhost;dbname=test',
 		'PDOTEST_USER' => getenv('PDO_DBLIB_TEST_USER') ?: 'php',
@@ -13,3 +13,11 @@ return [
 	],
 	'TESTS' => __DIR__ . '/ext/pdo/tests',
 ];
+
+if (getenv('PDO_DBLIB_TEST_DSN') === false) {
+	$config['ENV']['PDOTEST_SKIP_ATTR'] = serialize([
+		Pdo\Dblib::ATTR_CONNECTION_TIMEOUT => 1,
+	]);
+}
+
+return $config;
diff --git a/ext/pdo_dblib/tests/config.inc b/ext/pdo_dblib/tests/config.inc
index 1612a80a9336..d33a71b4245b 100644
--- a/ext/pdo_dblib/tests/config.inc
+++ b/ext/pdo_dblib/tests/config.inc
@@ -1,5 +1,7 @@
 <?php
 
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
+
 // bug #72969 reflects a bug with FreeTDS, not with pdo_dblib
 // this function will version detect so the relevant tests can XFAILIF
 // assume this bug isn't present if not using FreeTDS
@@ -41,15 +43,32 @@ function setAttributes(PDO $db) {
 }
 
 function getDbConnection(string $class = PDO::class, ?array $attributes = null) {
+    $connectionAttributes = $attributes;
+    $evaluatingSkipif = getenv('TEST_PHP_EVALUATING_SKIPIF') === '1';
+    if ($evaluatingSkipif && $connectionAttributes === null && getenv('PDO_DBLIB_TEST_DSN') === false) {
+        $connectionAttributes = [Pdo\Dblib::ATTR_CONNECTION_TIMEOUT => 1];
+    }
     [$dsn, $user, $pass] = getCredentials();
 
-    try {
-        $db = new $class($dsn, $user, $pass, $attributes);
-        if ($attributes === null) {
-            setAttributes($db);
+    $db = null;
+    $probe = static function () use (&$db, $class, $dsn, $user, $pass, $attributes, $connectionAttributes): ?string {
+        try {
+            $db = new $class($dsn, $user, $pass, $connectionAttributes);
+            if ($attributes === null) {
+                setAttributes($db);
+            }
+            return null;
+        } catch (PDOException $e) {
+            return $e->getMessage();
         }
-    } catch (PDOException $e) {
-        die('skip ' . $e->getMessage());
+    };
+
+    $reason = $evaluatingSkipif
+        ? ProbeCache::getFailure('pdo', [$class, false, $dsn, $user, $pass, $connectionAttributes], $probe)
+        : $probe();
+
+    if (is_string($reason)) {
+        die('skip ' . $reason);
     }
 
     return $db;
diff --git a/ext/pdo_mysql/tests/inc/mysql_pdo_test.inc b/ext/pdo_mysql/tests/inc/mysql_pdo_test.inc
index 75f299ff9e19..4e0c705f8e44 100644
--- a/ext/pdo_mysql/tests/inc/mysql_pdo_test.inc
+++ b/ext/pdo_mysql/tests/inc/mysql_pdo_test.inc
@@ -20,20 +20,29 @@ class MySQLPDOTest extends PDOTest {
             $attr = is_string($attr) && strlen($attr) ? unserialize($attr) : null;
         }
 
-        if ($useConnectMethod) {
-            $db = $classname::connect($dsn, $user, $pass, $attr);
-        } else {
-            $db = new $classname($dsn, $user, $pass, $attr);
+        if (getenv('TEST_PHP_EVALUATING_SKIPIF') !== '1') {
+            return self::createConnection($classname, $useConnectMethod, $dsn, $user, $pass, $attr);
         }
 
-        if (!$db) {
-            die("Could not create PDO object (DSN=$dsn, user=$user)\n");
-        }
+        $database = null;
+        $exception = null;
+        $configuration = [$classname, $useConnectMethod, $dsn, $user, $pass, $attr];
+
+        $reason = ProbeCache::getFailure('pdo', $configuration, static function () use (&$database, &$exception, $classname, $useConnectMethod, $dsn, $user, $pass, $attr): ?string {
+            try {
+                $database = self::createConnection($classname, $useConnectMethod, $dsn, $user, $pass, $attr);
+                return null;
+            } catch (PDOException $e) {
+                $exception = $e;
+                return $e->getMessage();
+            }
+        });
 
-        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
-        $db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
+        if (is_string($reason)) {
+            throw $exception ?? new PDOException($reason);
+        }
 
-        return $db;
+        return $database;
     }
 
     static function factoryWithAttr($attr) {
@@ -168,7 +177,7 @@ class MySQLPDOTest extends PDOTest {
 
     static function skip() {
         try {
-            $db = self::factory();
+            self::factory();
         } catch (PDOException $e) {
             die('skip could not connect');
         }
@@ -212,5 +221,22 @@ class MySQLPDOTest extends PDOTest {
         $message = $message ?? 'skip Transactional engine not found';
         if (false == self::detect_transactional_mysql_engine($db)) die($message);
     }
+
+    private static function createConnection($classname, bool $useConnectMethod, $dsn, $user, $pass, $attr) {
+        if ($useConnectMethod) {
+            $db = $classname::connect($dsn, $user, $pass, $attr);
+        } else {
+            $db = new $classname($dsn, $user, $pass, $attr);
+        }
+
+        if (!$db) {
+            die("Could not create PDO object (DSN=$dsn, user=$user)\n");
+        }
+
+        $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
+        $db->setAttribute(PDO::ATTR_CASE, PDO::CASE_LOWER);
+
+        return $db;
+    }
 }
 ?>
diff --git a/ext/pgsql/tests/inc/skipif.inc b/ext/pgsql/tests/inc/skipif.inc
index 2ce5f46e7787..bbe2a3169dd1 100644
--- a/ext/pgsql/tests/inc/skipif.inc
+++ b/ext/pgsql/tests/inc/skipif.inc
@@ -8,15 +8,22 @@
 
 include("config.inc");
 include("lcmess.inc");
+require_once dirname(__DIR__, 4) . '/tests/probe_cache.inc';
 
 if (getenv("SKIP_REPEAT")) {
     // pgsql tests are order-dependent.
     // We should probably change that, but in the meantime do not allow repetition.
     die("skip Cannot repeat pgsql tests");
 }
-$conn = @pg_connect($conn_str);
-if (!$conn) {
-    die("skip could not connect\n");
+$conn = null;
+
+$reason = ProbeCache::getFailure('pgsql', [$conn_str], static function () use (&$conn, $conn_str): ?string {
+    $conn = @pg_connect($conn_str);
+    return $conn ? null : 'could not connect';
+});
+
+if (is_string($reason)) {
+    die("skip $reason\n");
 }
 
 function skip_server_version($version, $op = '<')
diff --git a/ext/snmp/tests/skipif.inc b/ext/snmp/tests/skipif.inc
index 0ae4ee16e5b8..43cc75f36b73 100644
--- a/ext/snmp/tests/skipif.inc
+++ b/ext/snmp/tests/skipif.inc
@@ -1,10 +1,27 @@
 <?php
 require_once (dirname(__FILE__).'/snmp_include.inc');
+require_once dirname(__DIR__, 3) . '/tests/probe_cache.inc';
+
+function get_snmp_test_agent_unavailable_reason(): ?string
+{
+    global $hostname, $community, $timeout, $retries;
+
+    $probe = static fn(): ?string =>
+        @snmpget($hostname, $community, '.1.3.6.1.2.1.1.1.0', $timeout, $retries) === false
+            ? 'NO SNMPD on this host or community invalid'
+            : null;
+
+    $configuration = [$hostname, $community, $timeout];
+
+    return ProbeCache::getFailure('snmp', $configuration, $probe);
+}
 
 //test server is available
 // this require snmpget to work ...
 //snmpget  ( string $hostname  , string $community  ,
 //string $object_id  [, int $timeout  [, int $retries  ]] )
 
-if (@snmpget($hostname, $community, '.1.3.6.1.2.1.1.1.0', $timeout) === false)
-    die('skip NO SNMPD on this host or community invalid');
+$reason = get_snmp_test_agent_unavailable_reason();
+if (is_string($reason)) {
+    die("skip $reason");
+}
diff --git a/run-tests.php b/run-tests.php
index 998e7e24c337..7951ec7ae673 100755
--- a/run-tests.php
+++ b/run-tests.php
@@ -232,6 +232,8 @@ function main(): void
         }
     }
 
+    SharedProbeCache::setUp($environment);
+
     if (IS_WINDOWS && empty($environment["SystemRoot"])) {
         $environment["SystemRoot"] = getenv("SystemRoot");
     }
@@ -1065,13 +1067,68 @@ function get_file_cache_dir(): string
     return sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'php-run-tests-file-cache';
 }
 
+final class SharedProbeCache
+{
+    private string $directory;
+
+    private function __construct(string $directory)
+    {
+        $this->directory = $directory;
+    }
+
+    public static function setUp(array &$environment): void
+    {
+        unset($environment['TEST_PHP_SHARED_CACHE_DIR']);
+        if (getenv('TEST_PHP_SHARED_CACHE') === '0') {
+            return;
+        }
+
+        $cache = self::create();
+        if ($cache === null) {
+            return;
+        }
+
+        $environment['TEST_PHP_SHARED_CACHE_DIR'] = $cache->directory;
+        register_shutdown_function(static function () use ($cache): void {
+            $cache->cleanup();
+        });
+    }
+
+    private static function create(): ?self
+    {
+        $temporaryDirectory = sys_get_temp_dir();
+        if ($temporaryDirectory === '') {
+            return null;
+        }
+
+        for ($attempt = 0; $attempt < 3; $attempt++) {
+            $directory = $temporaryDirectory
+                . DIRECTORY_SEPARATOR
+                . 'php-run-tests-'
+                . bin2hex(random_bytes(8));
+            if (@mkdir($directory, 0700)) {
+                return new self($directory);
+            }
+        }
+
+        return null;
+    }
+
+    private function cleanup(): void
+    {
+        if (is_dir($this->directory)) {
+            rmdir_recursive($this->directory);
+        }
+    }
+}
+
 function rmdir_recursive($dir)
 {
-    if (!file_exists($dir)) {
+    if (!file_exists($dir) && !is_link($dir)) {
         return;
     }
-    if (!is_dir($dir)) {
-        unlink($dir);
+    if (is_link($dir) || !is_dir($dir)) {
+        @unlink($dir);
         return;
     }
 
@@ -3628,6 +3685,7 @@ public function checkSkip(string $php, string $code, string $checkFile, string $
         }
 
         save_text($checkFile, $code, $tempFile);
+        $env['TEST_PHP_EVALUATING_SKIPIF'] = '1';
         $result = trim(system_with_timeout("$php \"$checkFile\"", $env));
         if (strpos($result, 'nocache') === 0) {
             $result = '';
diff --git a/tests/probe_cache.inc b/tests/probe_cache.inc
new file mode 100644
index 000000000000..600308bd6994
--- /dev/null
+++ b/tests/probe_cache.inc
@@ -0,0 +1,52 @@
+<?php
+
+final class ProbeCache
+{
+    private const FAILURE_PREFIX = 'failure:';
+
+    /**
+     * Runs a probe once per configuration for the test run, caching only a
+     * failure. The callback returns its skip reason, or null on success.
+     */
+    public static function getFailure(string $namespace, array $configuration, callable $probe): ?string
+    {
+        $directory = getenv('TEST_PHP_SHARED_CACHE_DIR');
+        if (!is_string($directory) || !is_dir($directory)) {
+            return $probe();
+        }
+
+        $cacheFile = $directory
+            . DIRECTORY_SEPARATOR
+            . 'probe-'
+            . hash('sha256', serialize([$namespace, $configuration]));
+
+        $cache = @fopen($cacheFile, 'c+');
+
+        if ($cache === false || !flock($cache, LOCK_EX)) {
+            if (is_resource($cache)) {
+                fclose($cache);
+            }
+            return $probe();
+        }
+
+        try {
+            $cached = stream_get_contents($cache);
+            if (is_string($cached) && str_starts_with($cached, self::FAILURE_PREFIX)) {
+                return substr($cached, strlen(self::FAILURE_PREFIX));
+            }
+
+            $failure = $probe();
+            if (is_string($failure)) {
+                rewind($cache);
+                ftruncate($cache, 0);
+                fwrite($cache, self::FAILURE_PREFIX . $failure);
+                fflush($cache);
+            }
+
+            return $failure;
+        } finally {
+            flock($cache, LOCK_UN);
+            fclose($cache);
+        }
+    }
+}
diff --git a/tests/run-test/test_probe_cache.phpt b/tests/run-test/test_probe_cache.phpt
new file mode 100644
index 000000000000..70ad9ef7153e
--- /dev/null
+++ b/tests/run-test/test_probe_cache.phpt
@@ -0,0 +1,128 @@
+--TEST--
+Shared test probe cache caches failures across processes
+--FILE--
+<?php
+require dirname(__DIR__) . '/probe_cache.inc';
+
+function start_probe_cache_process(string $code, array $environment): array
+{
+    $command = getenv('TEST_PHP_EXECUTABLE_ESCAPED')
+        . ' -n -r '
+        . escapeshellarg($code);
+    $process = proc_open(
+        $command,
+        [
+            1 => ['pipe', 'w'],
+            2 => ['redirect', 1],
+        ],
+        $pipes,
+        null,
+        $environment,
+        ['bypass_shell' => true],
+    );
+
+    return [$process, $pipes];
+}
+
+function finish_probe_cache_process($process, array $pipes): string
+{
+    $output = stream_get_contents($pipes[1]);
+    fclose($pipes[1]);
+
+    if (0 !== $exitCode = proc_close($process)) {
+        throw new Exception("PHP subprocess exited with code $exitCode: $output");
+    }
+
+    return $output;
+}
+
+function run_probe_cache_process(string $code, array $environment): string
+{
+    [$process, $pipes] = start_probe_cache_process($code, $environment);
+    return finish_probe_cache_process($process, $pipes);
+}
+
+$cacheDirectory = getenv('TEST_PHP_SHARED_CACHE_DIR');
+if (!is_string($cacheDirectory)) {
+    throw new Exception('Missing shared test cache directory');
+}
+
+$environment = getenv();
+
+$helper = var_export(dirname(__DIR__) . '/probe_cache.inc', true);
+$namespace = 'probe-cache-test-' . bin2hex(random_bytes(8));
+$namespaceCode = var_export($namespace, true);
+$first = run_probe_cache_process(
+    "require $helper; echo ProbeCache::getFailure($namespaceCode, ['shared'], static fn(): ?string => 'shared failure');",
+    $environment,
+);
+$second = run_probe_cache_process(
+    "require $helper; echo ProbeCache::getFailure($namespaceCode, ['shared'], static function (): ?string { throw new Exception('Probe should not run'); });",
+    $environment,
+);
+echo "$first\n$second\n";
+
+$probeStarted = $cacheDirectory . '/probe_started';
+$probeStartedCode = var_export($probeStarted, true);
+@unlink($probeStarted);
+[$firstProcess, $firstPipes] = start_probe_cache_process(
+    "require $helper; echo ProbeCache::getFailure($namespaceCode, ['concurrent'], static function (): ?string { file_put_contents($probeStartedCode, 'started'); usleep(1000000); return 'concurrent failure'; });",
+    $environment,
+);
+
+$deadline = microtime(true) + 5;
+while (!file_exists($probeStarted) && microtime(true) < $deadline) {
+    usleep(1000);
+}
+if (!file_exists($probeStarted)) {
+    $output = finish_probe_cache_process($firstProcess, $firstPipes);
+    throw new Exception("Concurrent probe did not start: $output");
+}
+
+[$secondProcess, $secondPipes] = start_probe_cache_process(
+    "require $helper; echo ProbeCache::getFailure($namespaceCode, ['concurrent'], static function (): ?string { throw new Exception('Concurrent probe should not run'); });",
+    $environment,
+);
+$first = finish_probe_cache_process($firstProcess, $firstPipes);
+$second = finish_probe_cache_process($secondProcess, $secondPipes);
+echo "$first\n$second\n";
+
+putenv("TEST_PHP_SHARED_CACHE_DIR=$cacheDirectory");
+
+$failureCalls = 0;
+$failureProbe = static function () use (&$failureCalls): ?string {
+    $failureCalls++;
+    return "failure $failureCalls";
+};
+
+var_dump(ProbeCache::getFailure($namespace, ['first'], $failureProbe));
+var_dump(ProbeCache::getFailure($namespace, ['first'], $failureProbe));
+var_dump(ProbeCache::getFailure($namespace, ['second'], $failureProbe));
+var_dump($failureCalls);
+
+$successCalls = 0;
+$successProbe = static function () use (&$successCalls): ?string {
+    $successCalls++;
+    return null;
+};
+
+var_dump(ProbeCache::getFailure($namespace, ['available'], $successProbe));
+var_dump(ProbeCache::getFailure($namespace, ['available'], $successProbe));
+var_dump($successCalls);
+
+putenv('TEST_PHP_SHARED_CACHE_DIR');
+var_dump(ProbeCache::getFailure($namespace, ['uncached'], static fn(): ?string => 'uncached failure'));
+?>
+--EXPECT--
+shared failure
+shared failure
+concurrent failure
+concurrent failure
+string(9) "failure 1"
+string(9) "failure 1"
+string(9) "failure 2"
+int(2)
+NULL
+NULL
+int(2)
+string(16) "uncached failure"
diff --git a/tests/run-test/test_skipif_environment.phpt b/tests/run-test/test_skipif_environment.phpt
new file mode 100644
index 000000000000..8ccb69b0e508
--- /dev/null
+++ b/tests/run-test/test_skipif_environment.phpt
@@ -0,0 +1,14 @@
+--TEST--
+SKIPIF evaluation environment
+--SKIPIF--
+<?php
+if (getenv('TEST_PHP_EVALUATING_SKIPIF') !== '1') {
+    echo 'missing SKIPIF environment marker';
+}
+?>
+--FILE--
+<?php
+var_dump(getenv('TEST_PHP_EVALUATING_SKIPIF'));
+?>
+--EXPECT--
+bool(false)