Append a php variable at top of php file after the <?php open tag

i need to write a php variable at the top of php file after the php tah(

<?php开发者_运维问答
   $test = "this is a string";       
?>
After appending the variable, the above content shoud be like,
<?php
   $subscriptionId = "123456789";
   $test = "this is a string";
?>
 Could not make it work using fwrite. Please suggest solution

---

I hope you're not describing an editor usage problem. Otherwise I'd recommend a regular expression to achieve the insertion:

$php = file_get_contents("example.php");
$php = preg_replace("/(<[?]php\s+)/", '$1  $subscriptionId = "123";\n', $php);
file_put_contents("example.php", $php);

There's no filesystem function for in-place insertion. You can only completely overwrite the php script.

---

Use str_replace() and don't omit to set the 4th parameter to 1, otherwise all occurrences of "<?php" will be replaced:

$php = file_get_contents("example.php");
$php = str_replace("<?php", "<?php\n  $subscriptionId = \"123456789\";\n", $php, 1);
file_put_contents("example.php", $php);

---

If you want to do it at the webserver level, there's the php.ini auto_prepend_file parameter. With some judicious <File>/<Location> setup in a httpd.conf file, you can limit which .php files have this parameter applied.