Multiple methods for specifying whether a string is included in a php string

The content of this article introduces the various methods of whether the PHP string contains the specified string. Now I share it with you. Friends in need can refer to it

When writing programs, you often have to deal with strings. The most basic thing is to search for strings. To detect whether a string contains a specified string in PHP, you can use regular expressions. If you don’t understand regular expressions, there are several functions that can provide you with convenient.

1. strstr

The strstr() function searches for the first occurrence of one string within another string.
This function returns the rest of the string (from the matching point). Returns false if the searched string is not found.

The code is as follows:

<?php
 /*如手册上的举例*/
 $email = &#39;user@example.com&#39;;
 $domain = strstr($email, &#39;@&#39;);
 echo $domain;
 // prints @example.com
?>

2. stristr

The stristr() function finds the first occurrence of a string within another string.
If successful, return the remainder of the string (from the point of the match). If the string is not found, returns false.

It is used exactly the same as strstr. The only difference is that strstr is not case sensitive.

3.strpos

The strpos function returns a boolean value. Needless to say, FALSE and TRUE. Use "===" to make a judgment. The execution speed of strpos is faster than the above two functions. In addition, strpos has a parameter to specify the judgment position, but it is empty by default. It means to judge the entire string. The disadvantage is that the support for Chinese is not good.

Example 1

if(strpos('www.jb51.net','jb51') !== false){ 
 echo '包含jb51'; 
}else{
 echo '不包含jb51'; 
}

Example 2

$str= 'abc';
$needle= 'a';
$pos = strpos($str, $needle); // 返回第一次找到改字符串的位置，这里返回为1，若查不到则返回False

4. explode

Use explode to judge. The PHP judgment string contains the following code:

function checkstr($str){
 $needle ='a';//判断是否包含a这个字符
 $tmparray = explode($needle,$str);
 if(count($tmparray)>1){
  return true;
 } else{
  return false;
 }
}

5, substr For example, we need to determine whether the last character is the specified character

<?php
/*
$str1="<p>这是个winrar专用的dll然后下哦啊不错的dll文件，QlogWin32.dll</p>";
if(substr($str1,-8)==".dll</p>"){
echo substr($str1,0,-4);
}

6. substr_count counts the number of times "substring" appears in the "original string"

The substr_count() function is the number of times a small string appears in a large string:
$number = substr_count(big_string, small_string);
Just today we need a function to find a string, to determine the characters Whether the string big_string contains the string small_string, returns true or fasle;

After checking the manual for a long time, I couldn't find a ready-made function, so I thought that I could use the substr_count function to implement the code as follows:

function check_str($str, $substr)
{
 $nums=substr_count($str,$substr);
  if ($nums>=1)
  {
   return true;
  }
  else
  {
   return false;
  }
}

Super easy!

For specific details, you can look up related functions for advanced applications.

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