Summary of usage of PHP array and string conversion functions

The following is a detailed summary of the conversion functions between arrays and strings in php. Friends in need can refer to the following

1. Convert a string into an array
str_split() is used to convert a string into an array
Syntax:

str_split(string,length)
<SPAN style="COLOR: #333333"><SPAN style="FONT-SIZE: 12px"><SPAN style="FONT-FAMILY: 宋体">//</SPAN></SPAN></SPAN>string是必须的，是要分割的字符串；<SPAN style="FONT-SIZE: 12px"><SPAN style="FONT-FAMILY: 宋体; COLOR: #333333"><SPAN style="LINE-HEIGHT: 28px">
//length是可选的，规定每个数组元素的长度
</SPAN></SPAN></SPAN>

tips:
If length is less than 1, the str_split() function will return false.
If length is greater than the length of the string, the entire string will be returned as the only element of the array.
Example:

<?php
$str="www.baidu.com";
print_r(str_split($str));
?>

2. String splitting function
explode() function splits the string is an array.
Syntax:
explode(separator,string,limit)
//separator is required and specifies the basis for splitting the string, for example: " "(space) "| " "," etc.
//string is required and is the string to be operated on
//limit is optional and specifies the maximum number of array elements returned.
Example:

<?php
$types="doc|docx|ppt|pptx|xls|xlsx|zip|rar";
print_r(explode("|",$types));
?>

3. Convert an array into a string
Use the implode() function Combine array elements into a string
Syntax:

<PRE>implode(separator,array)

//seperator是可选的，规定数组元素之间放置的内容，默认是“”（空字符串）
//array是必须的，是要结合成字符串的数组

tips:虽然 separator 参数是可选的。但是为了向后兼容，推荐您使用使用两个参数。implode() 可以接收两种参数顺序。但是由于历史原因，explode() 是不行的。你必须保证 separator 参数在 string 参数之前才行。例子：

<?php
$arr = array(&#39;Hello&#39;,&#39;World!&#39;,&#39;Beautiful&#39;,&#39;Day!&#39;);
echo implode(" ",$arr);
?>

4. Find another character in the string
Use strpos() or strstr() function
The strpos() function returns the position of the first occurrence of a string in another string.
If the string is not found, return false.
Syntax:

strpos(string,find,start)
//string为必须，表示被搜索的字符串
//find为必须，表示被查找的字符串
//start可选。规定开始搜索的位置。

tip:
This function is case sensitive
Example:

<?php
$str="HellO neo";
$find1="O";
$find2="o";
echo strpos($str,$find1);
echo "<br/>";
echo strpos($str,$find2);
?>

Output result:

4
8

## 5. Intercept part of the characters in the string
substr() function returns part of the string
Syntax:

substr(string,start,length)
//string为必需，规定要返回其中一部分的字符串。
/*必需。规定在字符串的何处开始。
    正数 - 在字符串的指定位置开始
    负数 - 在从字符串结尾的指定位置开始
    0 - 在字符串中的第一个字符处开始
*/
/*可选。规定要返回的字符串长度。默认是直到字符串的结尾。
    正数 - 从 start 参数所在的位置返回
    负数 - 从字符串末端返回
*/

tips:
If start is a negative number and length is less than or equal to start, length is 0.
Example;

<?php
$str="Hello world!";
echo substr($str,0);
echo "<br/>";
echo substr($str,6,5);
?>

6. Get the string length
strlen() function is used to calculate characters The length of the string.
Example:

<?php
$str="Hello world!";
echo strlen($str);
?>

//The output result is 12

7. Convert the string to uppercase
strtoupper() function converts a string to uppercase.
Example:

<?php
$str="Hello world!";
echo strtoupper($str);
?>
//输出结果为：HELLO WORLD!

8. Convert the string to lowercase
strtolower## The #() function converts a string to lowercase. Example:

<?php
$str="Hello World!";
echo strtolower($str);
?>

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