Functions commonly used in php development

$createtime = date( "Y-m-d H:i:s" );echo"$createtime ";//时间

The time function outputs the current hour, minute and second. For example, this function can record the time of publishing an article and displaying the post in the data field.

 $h = is_null( $c );  //判断数据是不是空

Judge whether the data is empty. Usually this function parameter is placed in a variable. Judgment

 exit;//终止后面的程序

When this function is executed, the following code will not be executed

cookie( 'email' );//获取cookie

Get the cookie of the currently visited URL. The parameter is the string cookie name

  $vv=substr($valueStr,-43);//从后面截取43个字符	

Intercept the desired characters from the current string. Usually parameter 1 is placed in the variable string. Parameters 2 and 3 fill in where to intercept and how much to intercept. You can only fill in two parameters.

echo PHP_VERSION;if(version_compare(PHP_VERSION,'5.4.0')<0){exit
('您的PHP版本为'.PHP_VERSION.'！我们的程序要求是PHP版本不低于5.4.0
!');}//要求php版本5.4.0

Judge PHP Is the version consistent with the current PHP application? To use this function, just modify the PHP version string parameter. For example, if you change the parameter version of this case to 8.0, you must require version 8.0 or above to execute our website normally. If you use the management of this website If the member's server does not have the corresponding PHP version environment, our prompt will be output and all codes will not be executed.

$valueStr = '';	
foreach ( $a as $v ) {
$valueStr .= "" . $v[ 'images' ] . ""; //循环拼接添加数据数组转为
字符串   	}

This small traversal code is often used. For example, if you check the database, the object contains an array. At that time, you can traverse the forech parameter 2 in this way, that is, the obtained object contains an array and converted into a two-dimensional array. If you want to convert it into a string, you can also splice it like this. Usually, in this case, $v[''images] is a database Field Because $v has been converted into an array, you can directly access this field like this. Many times when doing development, we like to query the database information as a two-dimensional array because we need to do traversal rendering. This case is easy to understand

getcwd();//获取当前目录

This function can get all the current directory paths. Many frameworks do not have the original directory structure. We can use this function to get the directory and then splice a string to get the path you want

isset( $_POST[ 'email' ]  )//判断数组有没有定义

To determine whether this array is defined, the parameter is to put an array value, which can be a variable or the obtained value

echo strlen($valueStr);//获取字符串长度	

To get the number of parameters in the string, just put a variable string

$d=date('Y-m-d');	$dd=strtotime($d);//把普通时间转化为时间戳

Convert the time format year, month and day into the timestamp format

$vvc = end( $v );//获取最后一个数组的一条数据

Get the last key value of the array. The parameter is an array or a variable array

if ( !empty( $id[ 0 ] ) ) {
			
            }   //判断数据有没有

Judge whether the data exists

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