strpos()

(PHP 4, PHP 5, PHP 7)

查找字符串首次出现的位置

说明

返回$needle在$haystack中首次出现的数字位置。

参数

在该字符串中进行查找。

如果$needle不是一个字符串，那么它将被转换为整型并被视为字符的顺序值。

如果提供了此参数，搜索会从字符串该字符数的起始位置开始统计。如果是负数，搜索会从字符串结尾指定字符数开始。

返回值

返回 needle 存在于$haystack字符串起始的位置(独立于 offset)。同时注意字符串位置是从0开始，而不是从1开始的。

如果没找到 needle，将返回FALSE。

此函数可能返回布尔值FALSE，但也可能返回等同于FALSE的非布尔值。请阅读布尔类型章节以获取更多信息。应使用===运算符来测试此函数的返回值。

更新日志

范例

使用===

注释

Note:此函数可安全用于二进制对象。

参见

• stripos()查找字符串首次出现的位置（不区分大小写）
• strrpos()计算指定字符串在目标字符串中最后一次出现的位置
• strripos()计算指定字符串在目标字符串中最后一次出现的位置（不区分大小写）
• strstr()查找字符串的首次出现
• strpbrk()在字符串中查找一组字符的任何一个字符
• substr()返回字符串的子串
• preg_match()执行匹配正则表达式

WARNING
As strpos may return either FALSE (substring absent) or 0 (substring at start of string), strict versus loose equivalency operators must be used very carefully.
To know that a substring is absent, you must use: 
=== FALSE
To know that a substring is present (in any position including 0), you can use either of:
!== FALSE (recommended)
 > -1 (note: or greater than any negative number)
To know that a substring is at the start of the string, you must use: 
=== 0
To know that a substring is in any position other than the start, you can use any of: 
 > 0 (recommended)
!= 0 (note: but not !== 0 which also equates to FALSE)
!= FALSE (disrecommended as highly confusing)
Also note that you cannot compare a value of "" to the returned value of strpos. With a loose equivalence operator (== or !=) it will return results which don't distinguish between the substring's presence versus position. With a strict equivalence operator (=== or !==) it will always return false.

This is a function I wrote to find all occurrences of a string, using strpos recursively.

This is how you use it:

It is interesting to be aware of the behavior when the treatment of strings with characters using different encodings.

will output:
Warning: strpos(): Empty needle in /in/lADCh on line 3 
bool(false) 
bool(false) 
Warning: strpos(): Empty needle in /in/lADCh on line 7 
bool(false)
Note also that warning text may differ depending on php version, see https://3v4l.org/lADCh

when you want to know how much of substring occurrences, you'll use "substr_count".
But, retrieve their positions, will be harder.
So, you can do it by starting with the last occurrence :
function strpos_r($haystack, $needle)
{
  if(strlen($needle) > strlen($haystack))
    trigger_error(sprintf("%s: length of argument 2 must be 

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