ScopedPHPTimeout.php

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<?php
class ScopedPHPTimeout {
        protected $startTime; // float; seconds
        protected $oldTimeout; // integer; seconds
        protected $oldIgnoreAbort; // boolean

        protected static $stackDepth = 0; // integer
        protected static $totalCalls = 0; // integer
        protected static $totalElapsed = 0; // float; seconds

        /* Prevent callers in infinite loops from running forever */
        const MAX_TOTAL_CALLS = 1000000;
        const MAX_TOTAL_TIME = 300; // seconds

        public function __construct( $seconds ) {
                if ( ini_get( 'max_execution_time' ) > 0 ) { // CLI uses 0
                        if ( self::$totalCalls >= self::MAX_TOTAL_CALLS ) {
                                trigger_error( "Maximum invocations of " . __CLASS__ . " exceeded." );
                        } elseif ( self::$totalElapsed >= self::MAX_TOTAL_TIME ) {
                                trigger_error( "Time limit within invocations of " . __CLASS__ . " exceeded." );
                        } elseif ( self::$stackDepth > 0 ) { // recursion guard
                                trigger_error( "Resursive invocation of " . __CLASS__ . " attempted." );
                        } else {
                                $this->oldIgnoreAbort = ignore_user_abort( true );
                                $this->oldTimeout = ini_set( 'max_execution_time', $seconds );
                                $this->startTime = microtime( true );
                                ++self::$stackDepth;
                                ++self::$totalCalls; // proof against < 1us scopes
                        }
                }
        }

        public function __destruct() {
                if ( $this->oldTimeout ) {
                        $elapsed = microtime( true ) - $this->startTime;
                        // Note: a limit of 0 is treated as "forever"
                        set_time_limit( max( 1, $this->oldTimeout - (int)$elapsed ) );
                        // If each scoped timeout is for less than one second, we end up
                        // restoring the original timeout without any decrease in value.
                        // Thus web scripts in an infinite loop can run forever unless we
                        // take some measures to prevent this. Track total time and calls.
                        self::$totalElapsed += $elapsed;
                        --self::$stackDepth;
                        ignore_user_abort( $this->oldIgnoreAbort );
                }
        }
}