Five usage methods of the latest string interception function php str_replace in 2017 and detailed explanation of the function-PHP Tutorial-php.cn

Five usage methods of the latest string interception function php str_replace in 2017 and detailed explanation of the function

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Release： 2023-03-11 07:20:01

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Five usage methods of the latest string interception function php str_replace in 2017 and detailed explanation of the function

1.php preg_match_all结合str_replace替换内容中所有img

方法大致是：先读取内容里的所以IMG标签，然后把每个IMG标签的SRC抽取出来，并且组合成自己的内容，最后进行替换。
preg_match_all就是我想要的函数，它能够把正则表达式匹配到的内容建立一个三维数组，你可以对它们进行遍历查找替换，不太了解的请查查手册，这里不作具体介绍。函数代码：

function replace($str)
{
preg_match_all(”/<img(.*)(src=\”[^\"]+\”)[^>]+>/isU”, $str, $arr);
for($i=0,$j=count($arr[0]);$i<$j;$i++){
$str = str_replace($arr[0][$i],”<img alt=\”我的信息” “.$arr[2][$i].” />”,$str);
}
return $str;
}

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2. PHP 截取字符串函数 strtr/str_replace

1. strtr 转换指定字符

* string strtr ( string $str , string $from , string $to )
* string strtr ( string $str , array $replace_pairs )

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* 该函数返回 str 的一个副本，并将在 from 中指定的字符转换为 to 中相应的字符。

* 如果 from 与 to 长度不相等，那么多余的字符部分将被忽略。

3.关于str_replace_once怎么只替换内容不替换里面alt标签

public function str_replace_once($needle,$replace,$haystack) 
{
    $pos = strpos($haystack, $needle);
    if ($pos === false) 
    {
        return $haystack;
    }
 
    return substr_replace($haystack, $replace, $pos, strlen($needle));
}

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4.为什么str_replace返回的数据错误

例：替换英文逗号，空格字符，或者中文逗号

$str = &#39;正确,联系我们 goodsjob，goodsjob&#39;;
$reg = array(&#39;,&#39;,&#39; &#39;,&#39;，&#39; );
$strs = &#39;username like %&#39;.str_replace($reg,&#39;%, or username like %&#39;,$str).&#39;%&#39;;

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返回的数据是：username like %正确%,%, or username like %or%, or username like %username%, or username like %like%, or username like %%联系我们%, or username like %goodsjob%, or username like %goodsjob%，为什么呢？

正确的结果应该是：usernme like %正确%, or username like %联系我们%, or username like %goodsjob%

先把空格替换成其他字符 $str在替换的过程中，=》 %, or username like % ，这里面也存在满足你替换规则的字符串所以会影响到结果

       $str = &#39;正确,联系我们 goodsjob，goodsjob&#39;;     
       $str = str_replace(&#39; &#39;, &#39; &#39;, $str);     
       $reg = array(&#39;,&#39;,&#39;，&#39;," ");     
       $strs = &#39;username like %&#39;.str_replace($reg,&#39;%, or username like %&#39;,$str).&#39;%&#39;;

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5.敏感词替换算法，效率比str_replace高4倍（附6仟个敏感词）

function strtr_array(&$str,&$replace_arr) {
$maxlen = 0;$minlen = 1024*128;
if (empty($replace_arr)) return $str;
foreach($replace_arr as $k => $v) {
$len = strlen($k);
if ($len < 1) continue;
if ($len > $maxlen) $maxlen = $len;
if ($len < $minlen) $minlen = $len;
}
$len = strlen($str);
$pos = 0;$result = &#39;&#39;;
while ($pos < $len) {
if ($pos + $maxlen > $len) $maxlen = $len - $pos;
$found = false;$key = &#39;&#39;;
for($i = 0;$i<$maxlen;++$i) $key .= $str[$i+$pos]; //原文：memcpy(key,str+$pos,$maxlen)
for($i = $maxlen;$i >= $minlen;--$i) {
$key1 = substr($key, 0, $i); //原文：key[$i] = &#39;\0&#39;
if (isset($replace_arr[$key1])) {
$result .= $replace_arr[$key1];
$pos += $i;
$found = true;
break;
}
}
if(!$found) $result .= $str[$pos++];
}
return $result;
}

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