Efforts to accelerate PHP programs

The accelerated display of dynamic website content is very important. This article discusses several functions of PHP in depth, proposed solutions for PHP web page compression and buffering. I. introduced several functions that control PHP output. PHP4 adopts a buffer mechanism. Before you decide to send the function, all the content only exists in the buffer, instead of sending it directly to the browser, although it is very important to use the header and the content of the se Dynamic website for accelerated display, this article through in-depth discussion of several PHP functions, A solution for PHP web page compression and buffering is proposed.

I. introduce several functions that control PHP output.

PHP4 uses a buffer mechanism. Before you decide to send, all content is stored in the buffer, rather than directly sent to the browser. although you can use the header and setcookie functions, however, these two functions are just a little bit of "skill" compared to the powerful output functions ". Let's take a look at the true capabilities of these functions:

Void ob_start (void );
This function instructs the PHP processor to redirect all output to the internal buffer. after this function is called, no output will be made to the browser.

String ob_get_contents (void );
This function returns the output buffer to a string. you can send the accumulated output together to the browser. Of course, you must first turn off the buffer.

Int ob_get_length (void );
This function returns the length of the output buffer.

Void ob_end_clean (void );
This function clears and disables the buffer. You need to use this function before outputting data to the browser.

Void ob_implicit_flush ([int flag])
This function is used to control implicit buffering and purging. the default value is off. if it is enabled, the results of each print/echo or output command are sent to the browser.



II. Use output control to compress PHP output

Before you start, make sure that your PHP4 compilation supports Zlib.
First, initialize the output buffer:


Ob_start ();

Ob_implicit_flush (0 );


Then all output content is generated.


Print ("This example shows compressed output! ");



After the page is generated, use:

$ Contents = ob_get_contents ();

Ob_end_clean ();


We also need to check whether the browser supports data compression by checking "gzip, deflate" in the variable $ HTTP_ACCEPT_ENCODING:


If (ereg ('gzip, deflate', $ HTTP_ACCEPT_ENCODING )){

// Generate the content after gzip

} Else {

Echo $ contents;

}


The following describes how to generate gzip output:

// Tell the browser that gzip data is received.

Header ("Content-Encoding: gzip ");

// Display the gzip file header

// Once is enough

Echo "x1fx8bx08x00x00x00x00x00 ";

// Calculate the length and CRC check code

$ Size = strlen ($ contents );

$ Crc = crc32 ($ contents );

// Compress data

$ Contents = gzcompress ($ contents, 9 );



// Content cannot be output directly here, because CRC has not been written!

$ Contents = substr ($ contents, 0, strlen ($ contents)-4 );

Echo $ contents;


Gzip_PrintFourChars ($ Crc );

Gzip_PrintFourChars ($ Size );


Function gzip_PrintFourChars ($ Val ){

For ($ I = 0; $ I <4; $ I ++ ){

Echo chr ($ Val %256 );

$ Val = floor ($ Val/256 );

}

}




3. buffer PHP output

The buffer can be easily implemented in PHP4. let's look at the example:


// Generate a unique file name for the requested URI.

$ Cached_file = md5 ($ REQUEST_URI );


If ((! File_exists ("/cache/$ cached_file") | (! Is_valid ("/cache/$ cached_file "))){


Ob_start ();

Ob_implicit_flush (0 );


// Output the buffer here


$ Contents = ob_get_contents ();

Ob_end_clean ();


$ Fil = fopen ($ cached_file, "w + ");

Fwrite ($ fil, $ contents, $ strlen ($ contents ));

Fclose ($ fil );

}


Readfile ($ cached_file );



IV. Conclusion

The PHP output buffer function is very useful in script output operations. compressing the buffer can reduce the output time by 80%, which is used to access other data resources (such as databases or XML, it is also a good buffer mechanism.


Original Author: Albert
Original source: www.freelamp.com