php Flashcards
php: To render a string to a template, type
-?php echo “string”; ?>
php: The built in function for returning the date year is
date(“Y”) e.g.
-?php echo date(“Y”); ?>
php: For the server to render a page as php,
the filename must be .php
php: Files that get included in other templates are called
include files, and go in “includes” folder
php: To include another template into your current template, type
-?php include(“file/path.php”); ?>
php: To create a php variable, type
-?php>
$varName = “string”
?>
note: Must start with dollar
php: Variables that are rendered before an include file
can be referenced from within the file
php: To return get params, type
$_GET[“key”]
php: To create an if, if else statement, type
just like js
if (100 == 100) {
....
} else if (100 == 100) {
...
} else {
...
}
php: To check if there is a query string, type
isset($_GET[“key”])
e.g. if (isset($_GET[“key”])) {
…
}
php: If you reference a get param that does not exist
it shows an error on the page, so always use if isset($_GET[‘key’]) {}
php: To set a conditional class name, type
-?php if (100==100) { echo “ class-name”; } ?>
php: For variables used in conditionals, always set a
default value to avoid errors like
$varName = null;
php: an “and” conditional statement uses
double ampersand
php: To create a variable that holds an array, type
$arrayVar = array("value1", "value2");
$arrayVar = ["value1", "value2"];php: The final semicolon for an if statement goes
inside the curly brackets
php: To concatenate a string with a var type
“string” . $varName
php: To render a loop through an array, type
foreach($arrayVar as $item) {
echo “-li>” . $item . “-/li>”;
}
php: To append an item to an existing array, type
$arrayVar[] = “string”;
php: To specify the key for an array item you are appending, type
$arrayVar[100] = “string”;
php: To return the length of an array, type
count($arrayVar);
php: in a foreach, the echo goes
inside the curly braces
php: A dictionary in php is called
an associative array
php: To create an associative array, type
$assArrayVar = [“key” => “value”, “key” => “value”]
php: Functions are usually
stored together in a functions.php file and included on all pages
php: To create a function, type
-?php
function function_name($param1, $param2) {
$output = $param1 . $param2;
return $output;
}
?>php: To pull out the id of an $item in a foreach, type
foreach ($arrayVar as $id => $item) {
echo $id . $item
}
php: To make a ternary operator/one line if, type
($varName == 10 ? true : false);
php: To return a random item key from an array, type
array_rand($arrayVar, 1);
note: the second argument is the number of items will be returned
php: To print a variable’s data to the screen, type
var_dump($varName);
php: To convert a string to lower case, type
strtolower(“string”)
php: To cut a specific string from the left, type
ltrim(“string”)
php: To sort an array in place, type
asort($arrayVar)
php: To make an “or” conditional statement, use
OR or ||
php: To make true or false the opposite, type
!true !false
php: To redirect, type
header(“location:page_name.php”);
exit;
note: Exit prevents other processes from occurring during redirect.
php: header(“location:page_name.php”) will fail if
there is anything sent back to the browser, so header() must be called in a php block at the very top of the page requested, and no blank lines can be above.
php: To convert an array to a string with spaces between each item, type
implode(“ “, $arrayVar);
php: To access params that are posted to a php endpoint, type
$_POST[“key”]
php: A short hand for appending something to an existing variable is
.=
php: To write a comment, typ
//
php: To make a route that accepts a form post
create a file and post the data to it (can be same as form). In target file, perform the actions you want on the data and then redirect to a thank you page in order to prevent the user from being able to refresh and resubmit a form.
php: To conditionally handle only a post or get request, type
if ($_SERVER[“REQUEST_METHOD”] == “POST”) {}
if ($_SERVER[“REQUEST_METHOD”] == “GET”) {}
php: When creating a condition that depends on a value of a request param, use
if (isset($_GET[“key”]) dbl amp $_GET[“key”]==”value”) {
…
}
To check the presence and value in one line
php: You can open an if else
in one area of the page and then close the if else inside of a php block that is not connected later in the page
php: To eliminate white space from a string, type
trim($varName)
php: To stop processing all code while handling a request, type
exit;
e.g.
if ($varName == "") {
echo "error"
exit;
}
note: If there was any html above this code, it would have sent by now
php: To clean up a user’s input for a form in the post request.
$name = trim(filter_input(INPUT_POST, “name”, FILTER_SANITIZE_STRING));
$email = trim(filter_input(INPUT_POST, “email”, FILTER_SANITIZE_EMAIL));
$message = trim(filter_input(INPUT_POST, “message”, FILTER_SANITIZE_SPECIAL_CHARS));
php: A good php email library is called
phpmailer
php: The difference between require “file.php” and include(“file.php”) is
if you include a file that doesn’t exist it will throw a warning and continue to execute code while require will error and quit.
php: To prevent getting an error when you require or include a file containing functions more than once
use include_once(“”) or require_once “”
note: require or include are more common to use in all cases
php: To create a class instance, type
@instanceName = new ClassName;
php: To call a class method, type
@instanceName->methodName(param1);
php: To call an object property, type
@instanceName->propertyName;
wp: To redirect user that is not logged in to the login page, type
if ( !is_user_logged_in() ) {
auth_redirect();
}
wp: To check if user is logged in, type
is_user_logged_in()
wp: The two types of hooks are
actions and filters. Filters must return and action don’t.
wp: An action is
a function you make that gets triggered by wp at a designated time.
wp: A filter is a
function that receives params from wp and must return something
wp: When wp runs its runtime, it
gets values of things by calling their hook which cause all of the functions associated with that hook to run and the return of the last hook that runs will be the value
wp: To run your hooked filter functions, type
apply_filters(“hook_name”, “default_param”)
note: apply_filters requires a default argument to be sent into the functions
wp: To create a filter that overwrites a default filter you must
add it to the same hook but make its priority a higher number so it runs after.
wp: To hook my filter onto a hook, type
add_filter(“hook_name”, “my_function_name”, 10, 1)
the 10 is priority, and 1 is number of arguments to accept. You know the number of args by checking the apply_filters() for this hook and seeing how many args it has (after the default value which would be the first argument)
wp: To create a filter function, type
function filter_function_name($arg) {
return ...
}
note: Make sure to accept an argument for filters. The argument is whatever is sent from apply("hook_name", "argument")wp: To remove a filter from a hook to prevent it from running, type
remove_filter(“hook_name”, “function_to_remove_name”, 10)
note: 10 is the priority that the function has, so you must check for it’s priority in the docs
wp: To check if a filter exists, type
has_filter(“filter_name”)
wp: To check if a filter has a function in it, type
has_filter(“filter_name”, “function_name”)
wp: To return true if you are in the main query, type
is_main_query()
wp: To return the type of page you are on, type
get_post_type()
wp: To remove an item from an array by its key, type
unset($arrayVar[“key”]);
wp: Essentially, the process of modifying wordpress is
create a function, hook it to a the right hook,
php: To cast a var to a type, type
(int)$varName or settype($foo, "int");
php: To pass params to an anonymous function, type
function() use ($param1, $param2) {
...
}php: To remove an action, type
remove_action(“hook_name”, “function_to_remove_name”, 10)
note: 10 is the priority
php: To add an action, type
add_filters(“hook_name”, “my_function_name”, 10, 1)
the 10 is priority, and 1 is number of arguments to accept. You know the number of args by checking the apply_actions() for this hook and seeing how many args it has (after the default value which would be the first argument to apply_actions())
wp: To create an action hook
create a function that holds the hook
function function_name() {
do_action("hook_name")
}
and call it from the page being loaded by the request
-?php echo function_name() ?>
wp: To check if an action hook has a certain function, type
has_action(“hook_name”, “function_name”)
wp: The hook that runs when widget get set up is called
widget_init
wp: The hook that runs when wp menus get set up is called
init
wp: It’s crucial to
attach to the correct hook for whatever you want to change
wp: wp provides a function that allows you to create new users called
$user_id = wp_insert_user()
note: Takes in an associative array and returns the user id
wp: To add a user meta to a user, type
update_user_meta( $user_id, ‘key’, ‘value’ )
