In PHP, when we want to replace specified characters in a string, we usually replace them all at once, such as the str_replace function, but sometimes we only want to replace the first occurrence, such as replacing keywords in an article. This cannot appear if there are 100 of them. 100 times, I just want to limit it a few times. Let me introduce to you how to achieve it.
Example
$str='This is a string. I only replace ABC once and I don’t replace the following ABC. Is there any way to achieve this? ';
Replace the first abc with xyz. Since the string to be replaced is fixed, many people think of using the str_replace() function to see if the use of this function is what we want
str_replace( mixed $search , mixed $replace , mixed $subject [, int &$count ] )
I accidentally thought that was what we wanted. The last parameter is to return the total number of replacements. It is a reference variable, not what I want to specify how many times it will be replaced, so use str_replace( ) is not possible
preg_replace() can be implemented, but it’s a pity that regular expressions are used,
The code is as follows | Copy code | ||||
echo $str;
|
Display email as starting from the first 2 digits of @ (inclusive) and hiding 4 digits forward
代码如下 | 复制代码 |
function show_email_2($string){ 有没有不用正则的,嗯可以这样 $replace='xyz'; |
The code is as follows | Copy code |
function show_email_2($string){ $first = strpos($string, '@'); //var_dump($first); if($first==1){ $string = '****'.$string; } If($first>1 && $first $string = substr_replace($string,'****',0,$first-1); } if($first>5){ $string = substr_replace($string,'****',$first-5,4); } var_dump($string); return $string; } //show_email_2('22@163.com'); //Output-->****2@163.com //show_email_2('22@22.com'); //Output-->****2@22.com Show_email_2('6123456@163.com'); //Output-->61****6@163.com Is there any way to use regular expressions? Yes, it can be like this $replace='xyz'; if(($position=strpos($str,$replace))!==false){ $leng=strlen($replace); $str=substr_replace($str,'abc',$position,$leng); } echo $str; |
If I want to replace to a specified number of times, please refer to the following method
The code is as follows
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Copy code
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||||
/* |
return rtrim($result_str,$word);
}
$text='hello world hello pig hello cat hello dog hello small boy';
$word='hello';
$cword='good-bye';
echo changeNstr($text,$word,$cword,3);
//Output: hello world hello pig good-bye cat hello dog hello small boy
?>

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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