PHP string learning: comparing two strings

In the previous article, we learned about the method of splicing two strings. If necessary, please read " Teach you how to use PHP operators to splice two strings together ". Today we will learn how to compare two strings, let’s learn together!

String comparison is a common operation in string processing. There are many ways to compare two strings in PHP. This article will introduce three common comparison methods through code examples:

Use comparison operators: == / === , > , etc.

Built-in function strcmp()

Built-in function strcasecmp()

1. Using the comparison operator

we can use == (double equal sign) or === (three equal sign) to compare strings for equality.

"; }else{ echo "两个字符串不相等 "; } if($str1===$str2){ echo "两个字符串相等 "; }else{ echo "两个字符串不相等 "; } ?> Output result: The difference between

两个字符串相等 两个字符串相等 ##== and === : == does not compare types, the triple equal sign ===, it does not convert types;

When using the equality (==) operator for comparison, if the two values are the same (it only compares variables value, not the data type), returns a true value; if the two values are not the same, returns a false value.

When comparing using the identity (===) operator, you look to see if two variables (expressions or constants) are equal in value and have the same data type, i.e. both are strings or both All are integers and so on. This operator returns true if two variables contain the same value and the same data type, otherwise it returns false.

We can use (less than) or > (greater than) to compare the size of strings. $str2){ echo "'$str1' 比 '$str2' 大 "; }else{ echo "'$str1' 比 '$str2' 小 "; } $str1="15"; $str2="13"; if($str1 "; }else{ echo "'$str1' 比 '$str2' 大 "; } ?>

Output result: '12' 比 '13' 小 '15' 比 '13' 大

PHP comparison operator list:

Comparison operator Name Description $a == $b Equal to If the values of $a and $b are equal after type conversion, return TRUE, otherwise return FALSE $a === $b Congruent If $a and $b are not only equal in value, but also their values The types are also equal, then TRUE is returned, otherwise FALSE is returned $a != $b is not equal to If $a is converted after type conversion If the value is not equal to the value of $b, it returns TRUE, otherwise it returns FALSE ##$a $b is not equal to and! = Same, if the value of $a is not equal to the value of $b after type conversion, TRUE is returned, otherwise FALSE is returned $a !== $b is incomplete etc If the value of $a is not equal to the value of $b, or the types of their values are different, return TRUE, otherwise return FALSE $a 小与 If the value of $a is less than the value of $b, return TRUE, otherwise return FALSE $a > $b Greater than If the value of $a is greater than the value of $b, return TRUE, otherwise return FALSE $a Less than or equal If the value of $a is less than or equal to the value of $b, return TRUE, otherwise return FALSE $a >= $ b Greater than or equal If the value of $a is greater than or equal to the value of $b, return TRUE, otherwise return FALSE ##$a $b Spaceship operator (combination comparison operator) When $a is less than, equal to, or greater than $b, it returns an integer value less than, equal to, or greater than 0 respectively. PHP7 starts to provide. $a ?? $b ?? $c NULL merge operator The first one exists from left to right And the operand is not NULL. If neither is defined and is not NULL, NULL is returned. Available starting with PHP7. 除了可以使用比较运算符来比较字符串外，还可以使用函数来比较字符串。PHP 中提供了两个函数来实现字符串比较功能，分别是 strcmp() 和 strcasecmp() 函数，我们来看看。

2、使用内置函数strcmp()--以区分大小写的方式比较两个字符串

strcmp(string1,string2) 比较两个字符串时，如果：

如果两个字符串相等，则会返回 0 ；

如果string1 小于 string2，则会返回 的值；

如果string1 大于 string2，则会返回 > 0 的值；

我们先来看下面一个例子：

";

$str1="12"; $str2="13"; echo strcmp($str1,$str2)." ";

$str1="15"; $str2="13"; echo strcmp($str1,$str2)." "; ?> 输出：

strcmp()函数在比较字符串时，是区分大小写的。

"; ?> 输出结果：

-1 借助这个特性，我们可以将其运用在网站注册账号时的确认用户密码功能中（密码通常是区分大小写的），比较两次输入的密码是否一致。

只有两个字符串完全匹配，strcmp()函数才会认为相等的；而在上面示例中，$pwd1 和 $pwd2的大小写不同，因此两个字符串不相等。

但有时，我们只需要比较字符串的值，不想区分大小写，例如比较网站的网址，那要怎么处理？简单，可以使用strcasecmp()函数。

3、使用内置函数strcasecmp()--以不区分大小写的方式比较两个字符串

strcasecmp()函数和strcmp()函数类似，都可比较字符串，返回值也相同，区别只是strcasecmp()函数不区分大小写。

下面我们来看看下面一个例子：

输出结果：

两个网址相同 好了就说到这里了，有其他想知道的，可以点击这个哦。→ → php视频教程

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PHP string learning: comparing two strings

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