PHP restore_error_handler() Function: Usage and Examples

Restores the previously active custom PHP error handler. This guide demonstrates its use in PHP code and explains when the result or side effect needs extra checks.

What It Does

Restores the previously active custom PHP error handler.

Syntax and Parameters

The examples below show a real call to restore_error_handler with suitable arguments. Read the function call in context: its connection, handle, input data or other prerequisites are created before use.

Requirements: standard PHP runtime with the named function available.

Example 1: Core Behavior

Register a handler before restoring it; do not expose original PHP error strings in HTTP responses.

<?php
set_error_handler(static function (int $level, string $message): bool {
    error_log('PHP error category ' . $level);
    return true;
});
restore_error_handler();
echo 'Previous handler restored';

Observe the returned value or changed resource state. A successful function call can still require additional checks before a higher-level operation is considered successful.

Example 2: Alternative or Failure Case

Register a handler before restoring it; do not expose original PHP error strings in HTTP responses.

<?php
set_error_handler(static function (int $level, string $message): bool {
    error_log('Handler layer 1: ' . $level);
    return true;
});
restore_error_handler();
echo 'Previous handler restored';

Compare the different inputs, environment assumptions or result checks. Do not use a transport-level success value as proof that all business-level requirements were met.

Practical Example: Applying the Rule

Register a handler before restoring it; do not expose original PHP error strings in HTTP responses.

<?php
set_error_handler(static function (int $level, string $message): bool {
    error_log('Handler layer 2: ' . $level);
    return true;
});
restore_error_handler();
echo 'Previous handler restored';

In an application, convert low-level failures into controlled responses and log only non-sensitive diagnostic context.

Important Behavior and Edge Cases

Handlers are stacked; calling without prior set_error_handler may restore default behavior.

Comparison with Related Functions or Patterns

Common Beginner Mistakes

Key Takeaways

• Restores the previously active custom PHP error handler.
• Handlers are stacked; calling without prior set_error_handler may restore default behavior.
• set_error_handler installs a custom handler.

Select this API or pattern based on its documented behavior and the trust boundaries in your own application, and test all external integrations against their actual deployments.