php: a guide

2026.02.20

installation

getting started

After you have installed php you can start a server using:

php -S localhost:8000

and you can navigate it using http://localhost:8000/filename.php

Perks and Quirks of php

Its case sensitive

format

php is defined inside a html format but as a tag <?php *code here* ?>

the file name for a php porgram is .php

heres a example code:

<!DOCTYPE html>
<html>
    <head>
        <title>Example</title>
    </head>
    <body>

        <?php
            echo "Hi, I'm a PHP script!";
        ?>

    </body>
</html>

variables

They are defined using $ keyword The good thing is that php handles the types and we dont have to define it.

$a = 20;
$b = 30;

$sum = $a - $b;

echo $sum;

data types

String
Integer
Float
Boolean
Array
NULL

$a = "Hi This is a String";
echo var_dump($a);

$b = "2232";
echo var_dump($b);

comments

just like css /* comment */

conditionals

if

if (condition) {
  then do this;
}

if-else

if (condition) {
  then do this;
} else {
  otherwise do this;
}

examples

marks

$marks = 80;

if ($marks >= 60) {
    echo "You have passed!";
} else {
    echo "You have failed.";
}

loops

for loops

for ($i=1;$i<=5;$i++) {
    echo $i;
}

for each (arrays)

foreach ($array as $value) {
    /* code here */
}

string functions

Function	Description
`strlen()`	Returns the length of a string (total number of characters)
`str_word_count()`	Counts the number of words in a string
`strrev()`	Reverses a string
`strpos()`	Searches for specific text and returns position of first match or false
`str_replace()`	Replaces some characters with other characters in a string
`substr()`	Returns a part of a string
`strtolower()`	Converts a string to lowercase
`substr_count()`	Counts the number of times a substring occurs in a string
`ucwords()`	Converts the first character of each word to uppercase
`trim()`	Removes whitespace from both sides of a string

$str = "   This is a example string   ";

echo "Original string:".$str."\n";

/* Functions */
echo "Length: ".strlen($str)."\n";
echo "Word Count: ".str_word_count($str)."\n";
echo "Reverse: ".strrev($str)."\n";
echo "Find text: ".strpos($str, "is")."\n";
echo "Replace: ".str_replace("example","php",$str)."\n";
echo "lowercase: ".strtolower($str)."\n";

arrays

/* only values */
$a = array(1, 5, 4, 9, 0);

/* keys and values */
$marks = array("english" => "75", "Maths" => "70", "Physics" => "80");

$a = array(1, 5, 4, 9, 8);

$b=0;
foreach ($a as $c) {
    $b=$b+$c;
}

echo $b;

$marks = array("english" => "69", "Maths" => "70", "Physics" => "80");

if ($marks["english"] == 69) {
    echo "You have scored ".$marks["english"]."(nice) in english";
} else {
    echo "You have scored ".$marks["english"]." in english";
}

functions

function($arg) {
    /* code */
}

function sum(int $x, int $y) {
    $z = $x + $y;

    return $z;
}

echo "5 + 8 = ".sum(5, 8);