imagecreate() returns an image identifier representing a blank image of size x_size by y_size.

echo -- Output one or more strings

Description

void echo ( string arg1 [, string argn...])

Outputs all parameters.

echo() is not actually a function (it is a language construct) so you are not required to use parentheses with it. In fact, if you want to pass more than one parameter to echo, you must not enclose the parameters within parentheses.

die -- Equivalent to exit()

Description

This language construct is equivalent to exit()

include()

The include() statement includes and evaluates the specified file.

The documentation below also applies to require(). The two constructs are identical in every way except how they handle failure. include() produces a Warning while require() results in a Fatal Error. In other words, use require() if you want a missing file to halt processing of the page. include() does not behave this way, the script will continue regardless. Be sure to have an appropriate include_path setting as well. Be warned that parse error in required file doesn't cause processing halting.

Files for including are first looked in include_path relative to the current working directory and then in include_path relative to the directory of current script. E.g. if your include_path is ., current working directory is /www/, you included include/a.php and there is include "b.php" in that file, b.php is first looked in /www/ and then in /www/include/.

When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward.

The switch statement is similar to a series of IF statements on the same expression. In many occasions, you may want to compare the same variable (or expression) with many different values, and execute a different piece of code depending on which value it equals to. This is exactly what the switch statement is for.

Note: Note that unlike some other languages, the continue statement applies to switch and acts similar to break. If you have a switch inside a loop and wish to continue to the next iteration of the outer loop, use continue 2.

print_r() displays information about a variable in a way that's readable by humans. If given a string, integer or float, the value itself will be printed. If given an array, values will be presented in a format that shows keys and elements. Similar notation is used for objects. print_r() and var_export() will also show protected and private properties of objects with PHP 5, on the contrary to var_dump().

Remember that print_r() will move the array pointer to the end. Use reset() to bring it back to beginning.

The if construct is one of the most important features of many languages, PHP included. It allows for conditional execution of code fragments. PHP features an if structure that is similar to that of C:

As described in the section about expressions, expr is evaluated to its Boolean value. If expr evaluates to TRUE, PHP will execute statement, and if it evaluates to FALSE - it'll ignore it. More information about what values evaluate to FALSE can be found in the 'Converting to boolean' section.

Returns the number of elements in var, which is typically an array (since anything else will have one element).

If var is not an array, 1 will be returned (exception: count(NULL) equals 0).

elseif, as its name suggests, is a combination of if and else. Like else, it extends an if statement to execute a different statement in case the original if expression evaluates to FALSE. However, unlike else, it will execute that alternative expression only if the elseif conditional expression evaluates to TRUE.

while loops are the simplest type of loop in PHP. They behave just like their C counterparts.

The meaning of a while statement is simple. It tells PHP to execute the nested statement(s) repeatedly, as long as the while expression evaluates to TRUE. The value of the expression is checked each time at the beginning of the loop, so even if this value changes during the execution of the nested statement(s), execution will not stop until the end of the iteration (each time PHP runs the statements in the loop is one iteration). Sometimes, if the while expression evaluates to FALSE from the very beginning, the nested statement(s) won't even be run once.

reset() rewinds array's internal pointer to the first element and returns the value of the first array element.

This function sorts an array such that array indices maintain their correlation with the array elements they are associated with. This is used mainly when sorting associative arrays where the actual element order is significant.

Returns TRUE on success or FALSE on failure.

Every array has an internal pointer to its "current" element, which is initialized to the first element inserted into the array.

The current() function simply returns the value of the array element that's currently being pointed to by the internal pointer. It does not move the pointer in any way. If the internal pointer points beyond the end of the elements list, current() returns FALSE.