Check: add regex()

src/Check.php

@@ -134,6 +134,31 @@ class Check {
     return false;
   }
 
+  /**
+   * Check value is a valid regex (PREG)
+   * @param mixed  $value          The value to check
+   * @param boolean $return_error  Set to true to get an error message about the error
+   * @return ( $return_error is true ? string|true : boolean )
+   */
+  public static function regex($value, $return_error=false) {
+    if (!is_string($value))
+      return $return_error?'PREG ERROR: not a string':false;
+    if (@preg_match($value, null) === false) {  // @phpstan-ignore-line
+      if ($return_error)
+        return sprintf(
+          'PREG ERROR #%d%s',
+          preg_last_error(),
+          (
+            function_exists('preg_last_error_msg')?
+            sprintf(" (%s)", preg_last_error_msg()):
+            ""
+          )
+        );
+      return false;
+    }
+    return true;
+  }
+
 }
 
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