How to determine image type by getting header information in php_PHP tutorial

How PHP determines the image type by obtaining header information,

This article describes the example of how PHP determines the image type by obtaining header information. Share it with everyone for your reference. The specific implementation method is as follows:

$filename = '617.gif' ; 
function pictype ( $file ) 
{ 
   /*$png_header = "/x89/x50/x4e/x47/x0d/x0a/x1a/x0a"; 
   $jpg_header = "/xff/xd8";*/
   $header = file_get_contents ( $file , 0 , NULL , 0 , 5 ); 
   //echo bin2hex($header); 
   if ( $header { 0 }. $header { 1 }== "/x89/x50" ) 
   { 
     return 'png' ; 
   } 
   else if( $header { 0 }. $header { 1 } == "/xff/xd8" ) 
   { 
     return 'jpeg' ; 
   } 
   else if( $header { 0 }. $header { 1 }. $header { 2 } == "/x47/x49/x46" ) 
   { 
     if( $header { 4 } == "/x37" ) 
       return 'gif87' ; 
     else if( $header { 4 } == "/x39" ) 
       return 'gif89' ; 
   } 
} 
echo pictype ( $filename );

I hope this article will be helpful to everyone’s PHP programming design.

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