Fix: Maximum execution time exceeded error in PHP

The ‘Maximum execution time exceeded’ error occurs when a PHP script runs longer than the allowed time limit. This error stops script execution and must be resolved for proper functionality.

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Common Causes and Fixes

1. Increase Time Limit

<?php
// ❌ Error: Script times out after 30 seconds
sleep(40);  // Error!
?>

<?php
// ✅ Fixed: Increase time limit
ini_set('max_execution_time', 60);  // 60 seconds
sleep(40);  // OK
?>

2. Infinite Loop

<?php
// ❌ Error: Infinite loop
while (true) {
    echo "Looping...";
}
?>

<?php
// ✅ Fixed: Proper loop condition
$count = 0;
while ($count < 10) {
    echo "Looping... $count";
    $count++;
}
?>

3. Large File Processing

<?php
// ❌ Error: Processing large file
$contents = file_get_contents('huge_file.txt');
$processed = strtoupper($contents);  // May timeout
?>

<?php
// ✅ Fixed: Process in chunks
$handle = fopen('huge_file.txt', 'r');
while (!feof($handle)) {
    $chunk = fread($handle, 8192);  // 8KB chunks
    $processed = strtoupper($chunk);
    // Process chunk
}
fclose($handle);
?>

4. Recursive Function Without Termination

<?php
// ❌ Error: Infinite recursion
function factorial($n) {
    return $n * factorial($n - 1);  // No base case
}
?>

<?php
// ✅ Fixed: Proper termination
function factorial($n) {
    if ($n <= 1) return 1;  // Base case
    return $n * factorial($n - 1);
}
?>

5. Database Query Timeout

<?php
// ❌ Error: Slow query
$stmt = $pdo->prepare("SELECT * FROM huge_table");
$stmt->execute();  // May timeout
$results = $stmt->fetchAll();
?>

<?php
// ✅ Fixed: Use pagination
$stmt = $pdo->prepare("SELECT * FROM huge_table LIMIT 1000");
$stmt->execute();
$results = $stmt->fetchAll();
?>

6. Unnecessary Processing

<?php
// ❌ Error: Heavy computation
for ($i = 0; $i < 10000000; $i++) {
    $result = expensive_calculation($i);  // Too slow
}
?>

<?php
// ✅ Fixed: Optimize or batch
for ($i = 0; $i < 1000000; $i += 1000) {
    $batch = array_slice(range($i, $i + 999), 0, 1000);
    foreach ($batch as $item) {
        $result = quick_calculation($item);
    }
}
?>

7. File Upload Processing

<?php
// ❌ Error: Processing large upload
if ($_FILES['file']['size'] > 10000000) {  // 10MB
    process_large_file($_FILES['file']['tmp_name']);  // May timeout
}
?>

<?php
// ✅ Fixed: Validate size first
if ($_FILES['file']['size'] > 10000000) {  // 10MB
    die("File too large");
}
process_file($_FILES['file']['tmp_name']);
?>

8. Using set_time_limit()

<?php
// ❌ Error: Default timeout
for ($i = 0; $i < 1000000; $i++) {
    process_item($i);
}
?>

<?php
// ✅ Fixed: Set time limit
set_time_limit(60);  // 60 seconds
for ($i = 0; $i < 1000000; $i++) {
    process_item($i);
}
?>

9. Progress Monitoring

<?php
// ❌ Error: No timeout handling
foreach ($large_array as $item) {
    process_item($item);
}
?>

<?php
// ✅ Fixed: Monitor and reset timer
$processed = 0;
foreach ($large_array as $item) {
    process_item($item);
    $processed++;
    
    if ($processed % 1000 === 0) {
        set_time_limit(30);  // Reset timer every 1000 items
    }
}
?>

10. Background Processing

<?php
// ❌ Error: Long process in web request
process_long_task();  // May timeout
echo "Done";
?>

<?php
// ✅ Fixed: Queue for background
queue_task('long_process');
echo "Task queued";
?>

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Quick Debugging Steps

1. Check script execution time with microtime()
2. Identify slow operations (loops, queries, file processing)
3. Verify time limit with ini_get('max_execution_time')
4. Use profiling tools to find bottlenecks
5. Test with smaller datasets

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Prevention Tips

• Set appropriate time limits: ini_set('max_execution_time', 30)
• Use set_time_limit(30) to reset timer
• Process large datasets in chunks
• Optimize database queries
• Avoid infinite loops and recursion
• Validate input size before processing
• Use background jobs for long tasks
• Monitor script performance

Remember: Increase execution time only as a temporary solution. Optimize code for better performance.