Php无限循环一遍又一遍？

Question

<?php

$offset = 0;
$find = "is";
$find_length = strlen($find);
$string = "This is a string, and it is an example.";

while($string_position = strpos($string, $find, $offset)){

echo $find. " Found at ". $string_position ."<br>";
$offset = string_position + find_length;

}


?>

keeping getting "is Found at 2" over and over . i am expecting " is found at 2", then 5, then 25

Answer 1

$offset = string_position + find_length;

Use variables instead of constants

$offset = $string_position + $find_length;

If the needle is found at the beginning of the string, strpos() returns 0, which means, that the loop will never start.

while(($string_position = strpos($string, $find, $offset)) !== false) {
  // code
}

Additional change your error settings in your development environment

error_reporting(E_ALL | E_STRICT);

Now you will get this as notice

PHP Notice:  Use of undefined constant string_position - assumed 'string_position' in php > shell code on line 4
PHP Stack trace:
PHP   1. {main}() php shell code:0

Notice: Use of undefined constant string_position - assumed 'string_position' in php shell > code on line 4

Call Stack:
    1.2172     636208   1. {main}() php shell code:0

PHP Notice:  Use of undefined constant find_length - assumed 'find_length' in php shell code on line 4
PHP Stack trace:
PHP   1. {main}() php shell code:0

Notice: Use of undefined constant find_length - assumed 'find_length' in php shell code on line 4

Call Stack:
    1.2172     636208   1. {main}() php shell code:0