how to debug php using developer tools code example

Example 1: php best debugging functions

<?php
$myVar = "hello world!";

var_dump($myVar);
print_r($myVar);

$allVars = get_defined_vars();
print_r($allVars);
debug_zval_dump($allVars);

function sayHello($hello) {
    echo $hello;
    debug_print_backtrace();
}

sayHello($myVar);
?>

Example 2: php best debugging functions

A good example of data output to the console via <script> tags, I myself used this first, but he broke the captcha job, because <script> tags were inserted into the base64 code of the captcha picture. Then I began to display logs in the headers with such a function (it may help someone else, in a similar situation):

<?php

function header_log($data){
  $bt = debug_backtrace();
  $caller = array_shift($bt);
  $line = $caller['line'];
  $file = array_pop(explode('/', $caller['file']));
  header('log_'.$file.'_'.$caller['line'].': '.json_encode($data));
}

?>

Usage:
$myvar = array(1,2,3);
header_log( $myvar ); // in headers we see: log_filename_rownumber: [1,2,3]