php知识点复习之正则表达式
//正则表达式的技术知识
// []定义字符集和 example [a-z] [a-z] [0-9] [\f\r\n\t]
//定位符^[a-z][0-9]$开头结尾
//量词 * + ? {n} {m,n} {n.}指的都是重复次数
//选择 |
//可打印字符：ascii中33-127表示的字符，就是我们看得见的符号 空格，删除，回车，取消等等就典型的是不可打印字符
//posox正则表达式
//常用函数
echo
;
$b4 = abc;
$pattern = [[:alpha:]];
echo ereg($pattern,$b4);
//输出1
//eregi() 无符号的
$b7 = asd&ass@ass&adfdf;
$pattern1 = &;
$pattern2 = [&@];
print_r(split($pattern1,$b7));
print_r(split($pattern2,$b7));
echo
;
$b8 = helloworld;
$pattern3 = world;
$replacement1 = persion;
echo ereg_replace($pattern3,$replacement1,$b8);
echo
;
echo sql_regcase(abcdefg);
//输出：[aa][bb][cc][dd][ee][ff][gg]
//perl 正则表达式 perl是在支持posix的基础上额外的扩展 \d数字 \d非数字 \s空白 \s非空白 \w字母数学符号下划线 \w非字母数字符号下划线
//常用函数array preg_grep ( string pattern, array input )
echo
;
$w1 = array(adad,adad4,asda,1asf3,sdfs);
$fl_array = preg_grep (/^\d{1,}$/, $w1);//此处强调一点{1,}而不是posix中的{1.}
print_r($fl_array);
echo
;
echo preg_match (/a/,abc);
//输出1
echo
;
//\b表示单词的边界
if (preg_match (/\bweb\b/i, php is the web scripting language of choice.)) {
print a match was found.;
} else {
print a match was not found.;
}
if (preg_match (/\bweb\b/i, php is the website scripting language of choice.)) {
print a match was found.;
} else {
print a match was not found.;
}
//尤其是在匹配电子邮箱是常用
echo
;
$pattern5 = /[\*]+/;
$w3 = aaa***bbb*ccc;
print_r(preg_split($pattern5,$w3));
echo
;
$pattern6 = /world/;
$content2 = girl;
$tre = hello world;
echo preg_replace($pattern6,$content2,$tre);
//string preg_quote ( string str [, string delimiter] )转义
echo
;
$keywords = $40 for a g3/400;
$keywords = preg_quote ($keywords, /);//此处的/若是不加，就不会转义g3/400中的/;
echo $keywords;