PHP基础学习笔记（常用函数）

字符串

strlen — 获取字符串长度

<?php
$str = 'abcdef';
echo strlen($str); // 6$str = ' ab cd ';
echo strlen($str); // 7
//strlen() 返回的是字符串的字节数，而不是其中字符的数量。
?>

strpos — 查找字符串首次出现的位置

$mystring = 'abc';
$findme   = 'a';
$pos = strpos($mystring, $findme);
echo $pos; //0// 忽视位置偏移量之前的字符进行查找
$newstring = 'abcdef abcdef';
$pos = strpos($newstring, 'a', 1); // $pos = 7, 不是 0
echo $pos; //7

str_replace — 子字符串替换

$bodytag = str_replace("%body%", "black", "<body text='%body%'>");
echo $bodytag; //<body text='black'>$vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
$onlyconsonants = str_replace($vowels, "", "Hello World of PHP");
echo $onlyconsonants; //Hll Wrld f PHP$phrase  = "You should eat fruits, vegetables, and fiber every day.";
$healthy = array("fruits", "vegetables", "fiber");
$yummy   = array("pizza", "beer", "ice cream");
$newphrase = str_replace($healthy, $yummy, $phrase);
echo $newphrase; //You should eat pizza, beer, and ice cream every day.$str = str_replace("ll", "", "good golly miss molly!", $count);
echo $count;//2$str     = "Line 1\nLine 2\rLine 3\r\nLine 4\n";
$order   = array("\r\n", "\n", "\r");
$replace = '<br />';
$newstr = str_replace($order, $replace, $str);
echo $newstr;//Line 1<br />Line 2<br />Line 3<br />Line 4<br />// 输出 F ，因为 A 被 B 替换，B 又被 C 替换，以此类推...
// 由于从左到右依次替换，最终 E 被 F 替换
$search  = array('A', 'B', 'C', 'D', 'E');
$replace = array('B', 'C', 'D', 'E', 'F');
$subject = 'A';
echo str_replace($search, $replace, $subject);//F$letters = array('a', 'p');
$fruit   = array('apple', 'pear');
$text    = 'a p';
$output  = str_replace($letters, $fruit, $text);
echo $output; //apearpearle pear

数组

count — 统计数组、Countable 对象中所有元素的数量

<?php
$a[0] = 1;
$a[1] = 3;
$a[2] = 5;
var_dump(count($a));//int(3)
$b[0]  = 7;
$b[5]  = 9;
$b[10] = 11;
var_dump(count($b));//int(3)
?>
<?php
$food = array('fruits' => array('orange', 'banana', 'apple'),'veggie' => array('carrot', 'collard', 'pea'));
// 递归计数
var_dump(count($food, COUNT_RECURSIVE)); //int(8)
// 常规计数
var_dump(count($food)); //int(2)
?>

explode — 使用一个字符串分割另一个字符串（字符串转数组）

<?php
// 示例 1
$pizza  = "piece1 piece2 piece3 piece4 piece5 piece6";
$pieces = explode(" ", $pizza);
echo $pieces[0]; // piece1
echo $pieces[1]; // piece2// 示例 2
$data = "foo:*:1023:1000::/home/foo:/bin/sh";
list($user, $pass, $uid, $gid, $gecos, $home, $shell) = explode(":", $data);
echo $user; // foo
echo $pass; // */*字符串内不包含分隔字符时，会简单返回只有一个原始字符串元素的 array。
*/
$input1 = "hello";
$input2 = "hello,there";
$input3 = ',';
var_dump( explode( ',', $input1 ) );
var_dump( explode( ',', $input2 ) );
var_dump( explode( ',', $input3 ) );$str = 'one|two|three|four';// 正数的 limit
print_r(explode('|', $str, 1)); //Array([0] => one|two|three|four)
print_r(explode('|', $str, 2)); //Array([0] => one [1] => two|three|four)// 负数的 limit
print_r(explode('|', $str, -1)); //Array([0] => one [1] => two [2] => three)
print_r(explode('|', $str, -2)); //Array([0] => one [1] => two)
?>

implode — 用字符串连接数组元素(数组转字符串)

<?php$array = ['lastname', 'email', 'phone'];
var_dump(implode(",", $array)); // string(20) "lastname,email,phone"// Empty string when using an empty array:
var_dump(implode('hello', [])); // string(0) ""// The separator is optional:
var_dump(implode(['a', 'b', 'c'])); // string(3) "abc"?>