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;

}


?>

一遍又一遍地“获得2”。我期待“发现在2”，然后是5，然后是25

Answer 1

$offset = string_position + find_length;

使用变量而不是常量

$offset = $string_position + $find_length;

如果在字符串的开头找到了针，strpos()会返回0，这意味着循环永远不会启动。

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

在开发环境中进行其他更改错误设置

error_reporting(E_ALL | E_STRICT);

现在你会得到这个通知

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

Answer 2

$符号遗失在：

$offset = string_position + find_length;

另外，一个小错误：如果在位置0找到字符串，循环将结束。

Answer 3

缺少一些$，请尝试：

$offset = $string_position + $find_length;