php知識點複習之正則表達式

//正則表達式的技術知識


//  []定義字符集和 example [a-z]  [A-Z]  [0-9] [\f\r\n\t]


//定位符^[A-Z][0-9]$開頭結尾


//量詞  *  +  ?  {n}  {m,n}  {n.}指的都是重複次數


//選擇 |


//可打印字符：ASCII中33-127表示的字符，就是我們看得見的符號 空格，刪除，回車，取消等等就典型的是不可打印字符


//POSiX正則表達式
//常用函數
echo "<br>";
$b4 = "abc";
$pattern = "[[:alpha:]]";
echo ereg($pattern,$b4);
//輸出1
//eregi()  無符號的

$b7 = "asd&ass@ass&adfdf";

$pattern1 = "&";
$pattern2 = "[&@]";
print_r(split($pattern1,$b7));
print_r(split($pattern2,$b7));


echo "<br>";
$b8 = "helloworld";
$pattern3 = "world";
$replacement1 = "persion";
echo ereg_replace($pattern3,$replacement1,$b8);


echo "<br>";
echo sql_regcase("abcdefg");
//輸出：[Aa][Bb][Cc][Dd][Ee][Ff][Gg]


//Perl 正則表達式 perl是在支持posix的基礎上額外的擴展 \d數字 \D非數字 \s空白 \S非空白 \w字母數學符號下劃線 \W非字母數字符號下劃線
 
//常用函數array preg_grep ( string pattern, array input )
echo "<br>";
$w1 = array("adad","adad4","asda","1asf3","sdfs");
$fl_array = preg_grep ("/^\D{1,}$/", $w1);//此處強調一點{1,}而不是posix中的{1.}
print_r($fl_array);


echo "<br>";
echo preg_match ("/a/","abc");
//輸出1


echo "<br>";
//\b表示單詞的邊界
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.";
}
//尤其是在匹配電子郵箱是常用


echo "<br>";
$pattern5 = "/[\*]+/";
$w3 = "aaa***bbb*ccc";
print_r(preg_split($pattern5,$w3));


echo "<br>";
$pattern6 = "/world/";
$content2 = "girl";
$tre = "hello world";
echo preg_replace($pattern6,$content2,$tre);


//string preg_quote ( string str [, string delimiter] )轉義
echo "<br>";
$keywords = "$40 for a g3/400";
$keywords = preg_quote ($keywords, "/");//此處的/若是不加，就不會轉義g3/400中的/;
echo $keywords;