php add 1 line to existing index.php

Question

I have some websites and I want to add a new code just after <?php I wrote this code but not works:

<?php
error_reporting(0);
$dir = __DIR__;
$index = $dir.'/index.php';

if (is_file($index)) {
    $content = file_get_contents($index);
    if (strpos($content, 'validator') === false) {
        str_replace('<?php', '<?php require_once \'path/validator.php\';', $content);
        
        //Write the index:
        $write = fopen($index,"w");
        fwrite($write,$content);
        fclose($write);
    }
    
    //Check again:
    $content = file_get_contents($index);
    if (strpos($content, 'validator') === true) {
        echo "Line added successfuly";
        unlink($dir.'/install.php');
    } else {
        echo "Line not added";
    }
}
?>

How can I do this? Thanks...

Answer 1

strpos() never returns true. It either returns a numeric index or false.

So change the second check to

if (strpos($content, 'validator') !== false)

By the way, you can use file_put_contents() to write the file in one step, just as you use file_get_contents() to read it.