php需要注意的点

<?php
$a ='e23i';
$b ='ab';
echo '---';
var_dump($a+$b);//0，重点
echo '---';
var_dump($a.$b);//e23iab
echo '---';
var_dump(implode('',array($a,$b)));//e23iab
echo '---';
var_dump("{$a}{$b}");//e23iab
echo '---';
$c ='https://outlook.live.com/mail/deleteditems';
var_dump( parse_url($c));
/*
*array(3) {
["scheme"]=>
string(5) "https"
["host"]=>
string(16) "outlook.live.com"
["path"]=>
string(18) "/mail/deleteditems"
}
*/
function xX($aa){
$aa = $aa+10;
return $aa;
}
$aa ='1';
var_dump( "Xx($aa)=".Xx($aa));//string(8) "Xx(1)=11"
class yy{
function __construct($a){
echo $a.'yy';
}
}
$b = new yY('xx');//xxyy 类名，方法名 不区分大小写，变量名区分大小写

$str ='cMMMCMde';
var_Dump(explode("M",$str));
/*
array(5) {
[0]=>
string(1) "c"
[1]=>
string(0) ""
[2]=>
string(0) ""
[3]=>
string(1) "C"
[4]=>
string(2) "de"
}
*/
var_dump(strrchr("Hello world!",'e'));
/*
string(11) "ello world!"
*/

$str = 'dir/upload.image.jpg';
var_dump(strrchr($str,'.'));
var_dump(substr($str,strrpos($str,'.')));
$arr = explode('.',$str);
var_dump(array_pop($arr));
var_dump( pathinfo($str,PATHINFO_EXTENSION));
$nstr = strrev($str);
var_dump(strrev(substr($nstr,0,strpos($nstr,'.'))));

/*

输出jpg扩展名

*/

/*二维数组排序*/

<?php
$data[] = array('volume' => 67, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 1,'e'=>3);
$data[] = array('volume' => 85, 'edition' => 6);
$data[] = array('volume' => 98, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 6);
$data[] = array('volume' => 67, 'edition' => 7);
// 取得列的列表
foreach ($data as $key => $row) {
$volume[$key] = $row['volume'];
$edition[$key] = $row['edition'];
}

// 将数据根据 volume 降序排列，根据 edition 升序排列
// 把 $data 作为最后一个参数，以通用键排序 SORT_ASC
array_multisort($volume, SORT_DESC ,$data);

var_dump($data);
/*

array(6) {
[0]=>
array(2) {
["volume"]=>
int(98)
["edition"]=>
int(2)
}
[1]=>
array(2) {
["volume"]=>
int(86)
["edition"]=>
int(6)
}
[2]=>
array(3) {
["volume"]=>
int(86)
["edition"]=>
int(1)
["e"]=>
int(3)
}
[3]=>
array(2) {
["volume"]=>
int(85)
["edition"]=>
int(6)
}
[4]=>
array(2) {
["volume"]=>
int(67)
["edition"]=>
int(2)
}
[5]=>
array(2) {
["volume"]=>
int(67)
["edition"]=>
int(7)
}
}
*/