PHP字符串

字符串

正则表达式

PHP支持POSIX和Perl两种正则表达式实现的特性和语法。

POSIX

略

perl

perl与JavaScript的正则表示风格一致，故采用perl版的正则表达式。

• preg_grep()

<?php $a=array("pasta","steak","fish","potatoes"); $food = preg_grep("/^p/",$a,1); //当传入第三个参数1时，输出不匹配的所有元素 print_r($food); //输出数组对应于输入数组的索引顺序 ?>

• preg_match();

<?php $text = "ticketre are $500."; preg_match("/a(re)/",$text,$match); print_r($match) ; //输出一个array("are","re") ?>

• preg_match_all()

<?php $text = "ticketre are $500."; preg_match_all("/a(re)/",$text,$match); print_r($match) ; //$match[0]内是所有与模式完全匹配的所有字符串的数组，$match[1]中含有所有与模式第一个小括号匹配的元素，以此类推 ?>

• preg_quote()

<?php $text = "ticket are $500."; echo preg_quote($text); //在对正则表达式而言有特殊含义的字符前插入一个反斜线 //输出为"ticket are \$500\." ?>

• preg_replace()

<?php $text = "this is a link to http://www.wilsonliu.cn/."; echo preg_replace("/http:\/\/(.*)\//","<a href=\"\${0}\">\${0}</a>",$text); ?>

//preg_replace还可以对数组进行替换
<?php $draft = "In 2007 the company faced plummeting revenues and scandal."; $keywords = array("/faced/","/plummeting/","/scandal/"); $replacements = array("celebrated","skyrocketing","expansion"); echo preg_replace($keywords,$replacements,$draft); ?>

• preg_replace_callback(pattern,callback,str)

<?php function acronym($matches){ $acronym = array( "WWW" => "World Wide Web", "IRS" => "Internal Revenue Service", "PDF" => "Portable Document Format" ); if(isset($acronym[$matches[1]])){ return $matches[1] . "(" . $acronym[$matches[1]] . ")"; }else { return $matches[1]; } } $text = "The <acronym>IRS</acronym>offers tax forms in <acronym>PDF</acronym>format on the <acronym>WWW</acronym>."; $newtext = preg_replace_callback("/<acronym>(.*)<\/acronym>/U","acronym",$text); print_r($newtext); //The IRS(Internal Revenue Service)offers tax forms in PDF(Portable Document Format)format on the WWW(World Wide Web). ?>

• preg_split()

<?php
$text = "wilson++++liu++++++tianna+++row";
$arr = preg_split("/\+{1,}/",$text);
foreach($arr as $p){
    echo $p . "\n";
}
?>

其他字符串函数

• strlen
• strcmp (区分大小写)
• strcasecmp(不区分大小写)
• strtolower() (全部转化为小写)
• strtoupper()(全部转化为大写)

正则表达式的替代函数

strtok 根据预定义的字符对字符串进行词法分析

<?php
$info = "wilson|world,china,change";
$tokens = ":|,";
$tokenized = strtok($info,$tokens);
while($tokenized){
    echo "log:$tokenized \n";
    $tokenized = strtok($tokens); //每次调用该函数只是对字符串的下一部分做词法分析，必须连续的调用该函数
}
?>

explode 根据预定义的定界符分解字符串

<?php $info = "wilson | world, china , change"; print_r(explode(" ",$info)); ?>

implode将数组转换为字符串

<?php $info = "wilson world china change"; $test = explode(" ",$info); print_r(implode("*",$test)); ?>

strpos(str,substr,offset) 找到substr在str中第一次出现的位置

strrpos(str,substr,offset) 找到substr在str中第一次出现的位置

str_replace 用另一个字符串替代字符串的所有实例

substr(str,start,len)

count_chars 字符串中字符计数

str_word_count()字符串中单词总数计数