PHP常用字符串函数用法实例总结

<?php
$str = 'a,b,c,d';
$res = explode(',',$str);
var_dump($res);

<?php
$arr = ['a'=>1,'b'=>2];
$res = implode(',',$arr);
var_dump($res);

<?php
$str = "A 'quote' is <b>bold</b>";
// 输出: A 'quote' is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str);

<?php
$str = "<p>this -&gt; &quot;</p>\n";
echo htmlspecialchars_decode($str);
//<p>this -> "</p>

<?php
$str = '   a';
$nstr = ltrim($str);
echo $nstr;

<?php
$str = 'abc';
$nstr = ltrim($str,'a');
echo $nstr;//返回去除后的结果

$str = "first=value&arr[]=foo+bar&arr[]=baz";
​
// 推荐用法
parse_str($str, $output);
echo $output['first']; // value
echo $output['arr'][0]; // foo bar
echo $output['arr'][1]; // baz

$str = '12311';
$res = str_replace('1','3',$str);
var_dump($res);

$str = 'hello';
$arr = str_split($str);
$arr1 = str_split($str,2);
var_dump($arr);
echo '<br>';
var_dump($arr1);
​
结果：
array(5) { [0]=> string(1) "h" [1]=> string(1) "e" [2]=> string(1) "l" [3]=> string(1) "l" [4]=> string(1) "o" } 
array(3) { [0]=> string(2) "he" [1]=> string(2) "ll" [2]=> string(1) "o" }

<?php
$email = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // 打印 @example.com  
​
返回此字符包括此字符的字符串

$user = strstr($email, '@', true); // 从 PHP 5.3.0 起
echo $user; // 打印 name
​
返回此字符之前的字符串

<?php
$str = '<p>hahaha</p>';
echo strip_tags($str);

<?php
$str = '<p><a href="">hahaha</a></p>';
echo strip_tags($str,'<a>');

  $findstr = 'a';
  $str = 'bca';
  $res = strpos($str,$findstr);
  var_dump($res);

$newstring = 'abcdef abcdef';
$pos = strpos($newstring, 'a', 0); // 这个0是偏移量，也就是第一次出现的位置，1就是第二次出现的位置
var_dump($pos);

<?php
$str = 'abc';
echo str_pad($str,5);
结果：
'abc '

<?php
$str = 'abc';
echo str_pad($str,10,"+");
结果：
abc+++++++

<?php
$str = 'abc';
echo str_pad($str,10,"+",STR_PAD_BOTH);

<?php
echo str_repeat("-", 10);
?>

<?php
$text = 'This is a Simple text.';
​
// 输出 "is is a Simple text."，因为 'i' 先被匹配
echo strpbrk($text, 'mi');

<?php
$text = 'This is a test';
echo substr_count($text, 'is'); // 2

$str = 'wo ca lie , zhe shi shen me gui';
​
$nstr = wordwrap($str,5,'<br/>');
​
echo $nstr;