PHP

Basics

Script language for dynamic web-pages. The syntax and concepts used are similar to Perl

Limited number of loops

 
for ($i = 0; $i <= 6; $i++) {
  echo "Loop number: $i ";
}

escapeshellcmd(shellcommand)

Return the shellcommand with everything that might confuse the shell escaped.

exec(<cmd>,<outputarray>,<returnvar>)

Executed <cmd> in the shell, append the command output to he array <outputarray> and set <returnvar> to the returnvalue of the command.

Also the last line of the command output is returned

shell_exec(<cmd>)

Execute <cmd> (output from excapedshellcmd) in the shell, return the command output.

date("Y-m-d h:i:s")

Current timestamp (YYYY-mm-dd HH:MM:SS).

Format "U" is unixtime (seconds since epoch)

sprintf("%7.2f", $float )

Format a number (7 digits, 2 decimals)

number_format($number, 2, '.', ',')

Format $number with 2 decimals, . as decimal separator and , as thousand separator.

strpos($string, $search,$start)

Return position of $search exists in $string. When it is not in, return FALSE. Start searching at position $start (optional). Simple test on strpos - if (strpos(x,y)) {} - does not differ between position 0 and FALSE. Test on position 2 or count from the end by setting $start to a negative value (possible since PHP7.1).

str_replace($old, $new, $string)

Return $string with $old replaced by $new

trim($string, 'abc')

Remove characters a, b and c from the start and the end of $string. If no characters are specified all whitespace will be removed.

round($float,<precision>)

Round $float to <precision> decimals (0 is default)

Regular expressions

PHP is Perl-like, patterns need delimiters (default is /<pattern>/ )

preg_match($pattern, $string)

Return 1 if $pattern exists in $string

preg_split('/\s*\=+\s*/',$string

Split $string into an array on a pattern (in this example on white-spaces and equality signs.

preg_replace('/#.*$/',,$string);

Replace matches with the pattern in $string (in this example to remove comments from a line)

Files

Almost all you need to know about files. For writing open with 'w' and fwrite($fh,$line)

$fh = fopen($filename, 'r') or die('Unable to open '.$file);
while(!feof($fh)) {
  $line =  fgets($fh);
}
fclose($fh)

Read directory

$dir = "./";

// Open a directory, and read its contents
if (is_dir($dir)){
  if ($dh = opendir($dir)){
    while (($file = readdir($dh))){
      echo "filename:" . $file . "\n";
    }
    closedir($dh);
  }
}

Functions

All variables are local to the function. You have to pass everything it needs, or declare variables as GLOBAL

function func1($arg1, $arg2)
{
    GLOBAL $vardeclaredoutside
    <codeblock>
    return $value;
}

Only one value can be returned but you can return arrays.

function func1()
{
    <codeblock>
    return array ($value1, $value2);
}

list($val1,$val2) = func1();

Arrays

arr = []

(Create) empty array

arr1 = [val1, val2, val3]

arr1 = array(val1, val2, val3)

Create an indexed array. The keys are the range 0..arraylength.

array_push($arr1,val1,val2)

Add elements val1 and val2 to the end of $arr1

$arr1 = array(key1=>val1, key2=>val2, key3=>val3)

$arr2[key1] = val1

Create an associative array (like a Perl#Hashes or a Python dictionay)

count($arr1)

Return the number of elements (length) of an array

end($arr1)

Return the value of the last element in $arr1 and set the pointer to it.

join(',',$arr1)

Join elements in arr1 with ',' as separator.

foreach($arr1 as $value) { codeblock }

Loop over an indexed array

foreach($arr1 as $key => $value) { codeblock }

Loop over an associative array

unset($arr1[key])

Remove the key element from $array. Numerical keys will not be reindexed.

Install

On debian (and its derivates)

apt-get install php-fpm php-mysql

Install php7 and mysql support

Fix php security by editing /etc/php/7.0/fpm/php.ini

Uncomment line with cgi.fix_pathinfo and set it to 0

php repository

apt -y install lsb-release apt-transport-https ca-certificates
wget -O /etc/apt/trusted.gpg.d/php.gpg https://packages.sury.org/php/apt.gpg
echo "deb https://packages.sury.org/php/ $(lsb_release -sc) main" | sudo tee /etc/apt/sources.list.d/php.list
sudo apt update
sudo apt -y install php7.4
php -v

Upgrade

Nice overview of how to upgrade can be found on php-watch

Installing multiple package can easily be done like install php8.3-{fpm,curl,mbstring,mysql,xml}