PHP - robbiehume/CS-Notes GitHub Wiki

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General

  • PHP is processed server side; need a server to run it
  • Browsers interact with the web server (Apache), which then runs the needed .php file by sending it to the PHP processor
    • The processor will run the .php file and make any necessary database calls and then return data to Apache
    • Then Apache sends it back to the browser
  • PHP is what's called a preprocessor: it processes on the server side before it sends it back
  • Most of the time PHP code is used to write out or output some kind of HTML, CSS, or JS code

Misc. Notes

  • var_dump()

Characteristics

  • Loosely typed

PHP tag:

  • When adding it inside HTML: <?php *code* ?>
  • When creating pure php file (no HTML just PHP): <?php *code* (no closing tag)

Including HTML:

  • <?php include “header.html” ?>
  • Helps make website more modulized

Syntax:

  • Must add semicolon at end (;)
  • Escaping PHP from HTML: separating PHP and HTML from each other to create cleaner code 
    • <p>This is a paragraph</p>
<?php
	echo "This is also a paragraph";
?>
<p>This is another paragraph</p>
  • Comments: // and /* */

User input form (@1:20:00) / URL parameters (@1:29:00):

  • $_GET["<name of HTML tag>"]
  • When an HTML form is submitted, it goes to the specified URL and passes the form data parameters

POST vs GET:

  • When GET is used for the HTML form method, it shows the values in the URL
  • When POST is used, it doesn’t show it in the URL
    • POST should be used when you have sensitive info that you’re using like a password or credit card number
    • In PHP, need to use $_POST instead of $_GET to retrieve the value

Data types:

10 primitive data types broken into 3 categories:

  • Scalar: string ('' or ""), integer, float, boolean (true or false)
  • Compound: array, object, callable, iterable
  • Special: resource, NULL

Variables:

  • Variables names start with $
    • $myVar = "var";
    • Same with referencing them: echo $myVar or echo "value: $myVar"
  • Constants:
    • CONST PI = 3.14;

String functions:

  • $str_var = “String”
  • strtoupper($str_var) // STRING; strtolower($str_var) // string
  • strlen($str_var) // 6
  • $str_var[1] // “t”
  • $str_var[5] = “G” // StrinG
  • str_replace(“St”, “sT”, $str_var) // sTring
  • substr($str_var, 3, 2) // in
  • String concatenation:
    • $a = “hello ”
    • $b = $a . “world” // “hello world”
    • $a .= “world” // “world world”

Arrays

  • $arr = array(“hi”, “hello”, 1, false)
  • $arr[4] = “yo” // $arr: “hi”, “hello”, 1, false, “yo”
  • echo $arr[4] // “yo”
  • echo count($arr) // 5

Using checkboxes:

  • Storing checkbox values in an array (@1:50:00)

Associative arrays (map / dictionary):

  • Can also store key/value pairs
  • $grades = array(“Jim”=>”A+”, “Pam”=>”B-“, “Oscar”=>”C+”)
  • echo $grades[“Jim”] // “A+”
  • $grades[“Jim”] = “F”
  • echo count($grades) // 3

Operators:

Equality:

  • == (!=) : implicitly cast and check if same value
    • 1 == "1"   // true
  • === (!==) : check if they are the same type and value
    • 1 === "1"  // false
  • Spaceship (<=>):
    • $x <=> $y returns:
      • 1 if left ($x) is greater than right ($y)
      • 0 if equal
      • -1 if right ($y) is greater than left ($x)

Logical:

  • and / &&
  • or / ||
  • xor: true only if one of the expressions is true, false otherwise (both true/false)

String operator (.):

  • Combine strings: 
    • $a = "My name is ";
$b = $a . "is Robbie";

Control structures:

Switch statement:

Classes and objects