How do you retrieve and save PHP variables using text files?

Answer 1

Saving and retrieving PHP variables to and from a text file is bad programming practice in most cases, and can have repercussions (for example, the possibility of a variable changing between any two times running a script, and the script not being prepared for the new value).

There are better alternatives available, such as using a database system like MySQL, or a more standardized "text file" system using INI files. See the related links for information on MySQL and INI files. With that in mind:

There are many routes to making a script that retrieves and saves PHP variables in a text file, but a simple and common one may use the functions file_get_contents and file_put_contents, along with others like preg_match.

file_get_contents($filename) can be used to get the variables (and any other content) in our text file.

file_put_contents($filename) can be used to save variables to our text file.

preg_match($pattern, $string) can be used to validate a string and see if it matches the specified pattern.

See the related links for more information on these variables.

Before actually writing the script, a format of writing our variables (and their values) should be planned out. Simply put, what should your text file look like? For this example, we'll assume a style like this:

var1 = "something"

var2 = TRUE

var3 = 59

The style rule we're going to use here is the name of a variable, followed by a space, an equal sign, and another space, then the PHP syntax of a variable value (var1 will be a string, var2 will be a boolean, var3 will be an integer, and such). A new line specifies a new variable declaration.

Now lets go ahead and write our script. The one in this example will be called "index.php", but any name will do.

index.php

// First, lay out where our text file is for future use

$path = 'vars.txt';

// Create a function that will take the contents of our text file and transform it into PHP variables

function get_vars() {// This allows us to access the path variable in this custom functionglobal $path;// Get the actual contents of the text file and put it in a variable$contents = file_get_contents($path);// Seperate the content line-by-line$contents = explode("\n", $contents);// Take each line and evaluate itforeach ($contents as $key=>$line) { // Check if the syntax of the line is correct with a regular expressionif (!preg_match('/^[^0-9][A-Za-z0-9_]* = (TRUE|FALSE|NULL|[0-9]*|".*")$/', $line) { // Stop the function so we don't parse any bad syntaxreturn FALSE;

}

// Divide the line by spaces; there should be three divisions

$divisions = explode(' ', $line);

// Now lets give the divisions their rightful names

$varname = $divisions[0];

$value = $divisions[2];

// Lets assign the variable in PHP depending on its value type

if ($value NULL) {$value = 'NULL';

}

elseif (is_int($value)) {$value = $value;

}

elseif (is_str($value)) {$value = '"' . $value . '"';

}

// If the value isn't formatted yet, the value cant be contained by our format

else {return FALSE;

}

// Add the formatted value to the line

$line .= $value;

// Add the line to the file's new content and then a new line

$content .= $line . "\n";

// Repeat this loop if there are more variables to add

}

// Now put the variables in the text file

if (!file_put_contents($path, $content)) {// Something went wrong with putting the content inreturn FALSE;

}

}

// Now play with the functions!

get_vars();

echo $var1; // echos "something" if using example text file from earlier

$var2 = FALSE;

$var3 = 60;

if (!save_vars('$var2,$var3')) {exit('Variables were not saved!');

}

exit('Variables were saved!');

?>

This is a very simple way of going about retrieving and saving PHP variables in text files; its not perfect.

If you're more experienced, toy around with the code and make it more advanced!