PHP ParseError

ParseError class extends CompileError class and is thrown when PHP code inside a string passed to the eval() function contains syntax errors.

The eval() function evaluates a given string as PHP code. If the code contains syntax errors, it throws a ParseError instead of causing a fatal error.

Syntax

eval ( string $code ) : mixed

Parameters

Valid code returns NULL, while syntax errors in the code throw a ParseError exception.

Example

The following example demonstrates how ParseError is thrown when invalid syntax is passed to eval() −

<?php
$a = 10;
try {
    eval('$a = $a + ;'); // Missing operand after +
} catch (ParseError $e) {
    echo "Parse Error: " . $e->getMessage();
}
?>

Parse Error: syntax error, unexpected ';'

Complete Example with Multiple Scenarios

Here's a more comprehensive example showing different ParseError scenarios −

<?php
function testParseError($code, $description) {
    echo "Testing: $description<br>";
    try {
        eval($code);
        echo "Success<br>";
    } catch (ParseError $e) {
        echo "ParseError: " . $e->getMessage() . "<br>";
    }
    echo "---<br>";
}

// Test cases
testParseError('$x = 5;', 'Valid syntax');
testParseError('$x = ;', 'Missing value');
testParseError('echo "Hello"', 'Missing semicolon');
testParseError('$x = 5 + ;', 'Incomplete expression');
?>

Testing: Valid syntax
Success
---
Testing: Missing value
ParseError: syntax error, unexpected ';'
---
Testing: Missing semicolon
ParseError: syntax error, unexpected end of file
---
Testing: Incomplete expression
ParseError: syntax error, unexpected ';'
---

Conclusion

ParseError provides a way to handle syntax errors in dynamically evaluated PHP code gracefully. Always use try-catch blocks when using eval() to prevent fatal errors and handle syntax issues properly.