转自https://www.cnblogs.com/sgm4231/p/9782271.html
php中常用的正则表达式函数
* preg_match()
* preg_match_all()
* preg_replace()
* preg_filter()
* preg_grep()
* preg_split()
* preg_quote()
接下来对比讲解：
讲解中 $pattern 通常表示正则表达式
$subject 通常表示目标处理数据
定义一个方法 方便查看数据类型：
function show($val = null)
if(empty($val))
//打印空
echo ‘null‘;
elseif(is_array($val) || is_object($val))
//打印数组或者对象
echo ‘<pre>‘;
print_r($val);
echo ‘</pre>‘;
else
//打印string int float
echo $val;
preg_match()与preg_match_all()
/*方法简单说明*/
preg_match($pattern,$subject,[array &$matches]) //匹配一次 第三个参数可选 匹配结果放置matches数组
preg_match_all($pattern,$subject,array &matches) //匹配多次 三参必选 匹配结果放置matches数组
$pattern = ‘/[0-9]/‘;
$subject=‘b5fg4sgf3sd2f1g‘;
$m1 =preg_match($pattern,$subject,$arr1);
show($m1);
show($arr1);
/*
1
Array
(
[0] => 5
)
*/
$m2 =preg_match_all($pattern,$subject,$arr2);
show($m2);
show($arr2);
/*
5
Array
(
[0] => Array
(
[0] => 5
[1] => 4
[2] => 3
[3] => 2
[4] => 1
)
)
*/
2.preg_replace()与preg_filter()
/*方法简单说明*/
* preg_replace与preg_filter
* preg_replace($pattern,$replacement,$subject)
* //正则替换函数被替换对象是数组 返回全部
//正则替换函数 被替换对象是数组 仅返回被替换元素
* 联想：str_repalce()
* echo str_replace("world","Shanghai","Hello world!");
* //得到Hello Shanghai!
//第一测 字符串中替换字符串 结论：此处preg_replace()与preg_filter()无区别
$pattern = ‘/[0-9]/‘;
$subject=‘b65fg4sgf3sd2f1g‘;
$replacement = ‘_‘;
$str1 = preg_replace($pattern,$replacement,$subject);
$str2 = preg_filter($pattern,$replacement,$subject);
echo ‘<hr>‘;
show($str1);
echo ‘<br>‘;
show($str2);
/*
b__fg_sgf_sd_f_g
b__fg_sgf_sd_f_g
*/
//第二测 字符串中根据数组正则 替换 结论：此处preg_replace()与preg_filter()无区别
$pattern = array(‘/[123]/‘,‘/[456]/‘,‘/[789]/‘);
$subject=‘b123fg3456sgf3789f1g‘;
$replacement = array(‘天‘,‘地‘,‘人‘);
$str3 = preg_replace($pattern,$replacement,$subject);
$str4 = preg_filter($pattern,$replacement,$subject);
echo ‘<hr>‘;
show($str3);
echo ‘<br>‘;
show($str4);
/*
b天天天fg天地地地sgf天人人人f天g
b天天天fg天地地地sgf天人人人f天g
*/
//第三测 数组中根据数组正则 替换 结论：此处展示preg_repalce()与preg_filter()有区别
$pattern = array(‘/[123]/‘,‘/[456]/‘,‘/[789]/‘);
$subject=array(‘b‘,‘fg3‘,‘456‘,‘sgf‘,‘789‘,‘fg‘);
$replacement = array(‘天‘,‘地‘,‘人‘);
$str5 = preg_replace($pattern,$replacement,$subject);
$str6 = preg_filter($pattern,$replacement,$subject);
echo ‘<hr>‘;
show($str5);
echo ‘<br>‘;
show($str6);
/*
Array
(
[0] => b
[1] => fg天
[2] => 地地地
[3] => sgf
[4] => 人人人
[5] => fg
)
Array
(
[1] => fg天
[2] => 地地地
[4] => 人人人
)
*/
3 . preg_grep($pattern, array $subject) //此处$subject只可以为一维数组
/*函数说明*/
preg_grep($pattern,array $input)//只可以匹配一维数组 返回匹配成功的数组元素
可以理解preg_grep()为阉割版 preg_filter()
只做了匹配 不作替换
$pattern = ‘/[0-9]/‘;
$subject=array(‘b‘,‘fg3‘,‘456‘,‘sgf‘,‘789‘,‘fg‘);
$arr = preg_grep($pattern,$subject);
show($arr);
/*
Array
(
[1] => fg3
[2] => 456
[4] => 789
)
*/
4 . preg_split($pattern,$subject)//一匹配成功为切割点切割字符串成数组
可以理解preg_split()升级版的explode()
$pattern = ‘/[0-9]/‘;
$subject=‘bfg3456sgf789fg‘;
$arr = preg_split($pattern,$subject);
show($arr);
/*
Array
(
[0] => bfg
[1] =>
[2] =>
[3] =>
[4] => sgf
[5] =>
[6] =>
[7] => fg
)
*/
5 . preg_quote($str) 正则运算符转译
/*
* preg_quote($str) 正则运算符转译
* . \\ + * ? [ ^ ] $ () = ! < > | : -
*
*/
echo ‘<hr>‘;
$str = "qewrasdf[123]";
$str =preg_quote($str);
print_r($str);
/*
qewr\\asdf\\\\[123\\]
*/
简单总结通性：
preg_ 开头
除preg_quote函数以外，第一个参数都是正则表达式
preg_match 表单验证等
preg_replace 非法词语过滤等
