php-the-right-way/pages/The-Basics.md

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The Basics

Comparison operators

Comparison operators are an often overlooked aspect of PHP, which can lead to many unexpected outcomes. One such problem stems from strict comparisons (the comparison of booleans as integers).

{% highlight php %}

<?php $a = 5; // 5 as an integer var_dump($a == 5); // compare value; return true var_dump($a == '5'); // compare value (ignore type); return true var_dump($a === 5); // compare type/value (integer vs. integer); return true var_dump($a === '5'); // compare type/value (integer vs. string); return false //Equality comparisons if (strpos('testing', 'test')) { // 'test' is found at position 0, which is interpreted as the boolean 'false' // code... } // vs. strict comparisons if (strpos('testing', 'test') !== false) { // true, as strict comparison was made (0 !== false) // code... } {% endhighlight %} * [Comparison operators](https://www.php.net/language.operators.comparison) * [Comparison table](https://www.php.net/types.comparisons) * [Comparison cheatsheet](https://phpcheatsheets.com/index.php?page=compare) ## Conditional statements ### If statements While using 'if/else' statements within a function or class method, there is a common misconception that 'else' must be used in conjunction to declare potential outcomes. However if the outcome is to define the return value, 'else' is not necessary as 'return' will end the function, causing 'else' to become moot. {% highlight php %} <?php function test($a) { if ($a) { return true; } else { return false; } } // vs. function test($a) { if ($a) { return true; } return false; // else is not necessary } // or even shorter: function test($a) { return (bool) $a; } {% endhighlight %} * [If statements](https://www.php.net/control-structures.if) ### Switch statements Switch statements are a great way to avoid typing endless if's and elseif's, but there are a few things to be aware of: - Switch statements only compare values, and not the type (equivalent to '==') - They iterate case by case until a match is found. If no match is found, then the default is used (if defined) - Without a 'break', they will continue to implement each case until reaching a break/return - Within a function, using 'return' alleviates the need for 'break' as it ends the function {% highlight php %} <?php $answer = test(2); // the code from both 'case 2' and 'case 3' will be implemented function test($a) { switch ($a) { case 1: // code... break; // break is used to end the switch statement case 2: // code... // with no break, comparison will continue to 'case 3' case 3: // code... return $result; // within a function, 'return' will end the function default: // code... return $error; } } {% endhighlight %} * [Switch statements](https://www.php.net/control-structures.switch) * [PHP switch](http://phpswitch.com/) ## Global namespace When using namespaces, you may find that internal functions are hidden by functions you wrote. To fix this, refer to the global function by using a backslash before the function name. {% highlight php %} <?php namespace phptherightway; function fopen() { $file = \fopen(); // Our function name is the same as an internal function. // Execute the function from the global space by adding '\'. } function array() { $iterator = new \ArrayIterator(); // ArrayIterator is an internal class. Using its name without a backslash // will attempt to resolve it within your namespace. } {% endhighlight %} * [Global space](https://www.php.net/language.namespaces.global) * [Global rules](https://www.php.net/userlandnaming.rules) ## Strings ### Concatenation - If your line extends beyond the recommended line length (120 characters), consider concatenating your line - For readability it is best to use concatenation operators over concatenating assignment operators - While within the original scope of the variable, indent when concatenation uses a new line {% highlight php %} <?php $a = 'Multi-line example'; // concatenating assignment operator (.=) $a .= "\n"; $a .= 'of what not to do'; // vs $a = 'Multi-line example' // concatenation operator (.) . "\n" // indenting new lines . 'of what to do'; {% endhighlight %} * [String Operators](https://www.php.net/language.operators.string) ### String types Strings are a series of characters, which should sound fairly simple. That said, there are a few different types of strings and they offer slightly different syntax, with slightly different behaviors. #### Single quotes Single quotes are used to denote a "literal string". Literal strings do not attempt to parse special characters or variables. If using single quotes, you could enter a variable name into a string like so: `'some $thing'`, and you would see the exact output of `some $thing`. If using double quotes, that would try to evaluate the `$thing` variable name and show errors if no variable was found. {% highlight php %} <?php echo 'This is my string, look at how pretty it is.'; // no need to parse a simple string /** * Output: * * This is my string, look at how pretty it is. */ {% endhighlight %} * [Single quote](https://www.php.net/language.types.string#language.types.string.syntax.single) #### Double quotes Double quotes are the Swiss Army Knife of strings. They will not only parse variables as mentioned above, but all sorts of special characters, like `\n` for newline, `\t` for a tab, etc. {% highlight php %} <?php echo 'phptherightway is ' . $adjective . '.' // a single quotes example that uses multiple concatenating for . "\n" // variables and escaped string . 'I love learning' . $code . '!'; // vs echo "phptherightway is $adjective.\n I love learning $code!" // Instead of multiple concatenating, double quotes // enables us to use a parsable string {% endhighlight %} Double quotes can contain variables; this is called "interpolation". {% highlight php %} <?php $juice = 'plum'; echo "I like $juice juice"; // Output: I like plum juice {% endhighlight %} When using interpolation, it is often the case that the variable will be touching another character. This will result in some confusion as to what is the name of the variable, and what is a literal character. To fix this problem, wrap the variable within a pair of curly brackets. {% highlight php %} <?php $juice = 'plum'; echo "I drank some juice made of $juices"; // $juice cannot be parsed // vs $juice = 'plum'; echo "I drank some juice made of {$juice}s"; // $juice will be parsed /** * Complex variables will also be parsed within curly brackets */ $juice = array('apple', 'orange', 'plum'); echo "I drank some juice made of {$juice[1]}s"; // $juice[1] will be parsed {% endhighlight %} * [Double quotes](https://www.php.net/language.types.string#language.types.string.syntax.double) #### Nowdoc syntax Nowdoc syntax was introduced in 5.3 and internally behaves the same way as single quotes except it is suited toward the use of multi-line strings without the need for concatenating. {% highlight php %} <?php $str = <<<'EOD' // initialized by <<< Example of string spanning multiple lines using nowdoc syntax. $a does not parse. EOD; // closing 'EOD' must be on its own line, and to the left most point /** * Output: * * Example of string * spanning multiple lines * using nowdoc syntax. * $a does not parse. */ {% endhighlight %} * [Nowdoc syntax](https://www.php.net/language.types.string#language.types.string.syntax.nowdoc) #### Heredoc syntax Heredoc syntax internally behaves the same way as double quotes except it is suited toward the use of multi-line strings without the need for concatenating. {% highlight php %} <?php $a = 'Variables'; $str = << It should be noted that multiline strings can also be formed by continuing them across multilines in a statement. _e.g._ {% highlight php %} $str = " Example of string spanning multiple lines using statement syntax. $a are parsed. "; /** * Output: * * Example of string * spanning multiple lines * using statement syntax. * Variables are parsed. */ {% endhighlight %} ### Which is quicker? There is a myth floating around that single quote strings are fractionally quicker than double quote strings. This is fundamentally not true. If you are defining a single string and not trying to concatenate values or anything complicated, then either a single or double quoted string will be entirely identical. Neither are quicker. If you are concatenating multiple strings of any type, or interpolate values into a double quoted string, then the results can vary. If you are working with a small number of values, concatenation is minutely faster. With a lot of values, interpolating is minutely faster. Regardless of what you are doing with strings, none of the types will ever have any noticeable impact on your application. Trying to rewrite code to use one or the other is always an exercise in futility, so avoid this micro-optimization unless you really understand the meaning and impact of the differences. * [Disproving the Single Quotes Performance Myth](https://www.npopov.com/2012/01/09/Disproving-the-Single-Quotes-Performance-Myth.html) ## Ternary operators Ternary operators are a great way to condense code, but are often used in excess. While ternary operators can be stacked/nested, it is advised to use one per line for readability. {% highlight php %} <?php $a = 5; echo ($a == 5) ? 'yay' : 'nay'; {% endhighlight %} In comparison, here is an example that sacrifices all forms of readability for the sake of reducing the line count. {% highlight php %} <?php echo ($a) ? ($a == 5) ? 'yay' : 'nay' : ($b == 10) ? 'excessive' : ':('; // excess nesting, sacrificing readability {% endhighlight %} To 'return' a value with ternary operators use the correct syntax. {% highlight php %} <?php $a = 5; echo ($a == 5) ? return true : return false; // this example will output an error // vs $a = 5; return ($a == 5) ? 'yay' : 'nope'; // this example will return 'yay' {% endhighlight %} It should be noted that you do not need to use a ternary operator for returning a boolean value. An example of this would be: {% highlight php %} <?php $a = 3; return ($a == 3) ? true : false; // Will return true if $a == 3 or false // vs $a = 3; return $a == 3; // Will return true if $a == 3 or false {% endhighlight %} This can also be said for all operations(===, !==, !=, == etc). #### Utilising brackets with ternary operators for form and function When utilising a ternary operator, brackets can play their part to improve code readability and also to include unions within blocks of statements. An example of when there is no requirement to use bracketing is: {% highlight php %} <?php $a = 3; return ($a == 3) ? "yay" : "nope"; // return yay if $a == 3 or nope // vs $a = 3; return $a == 3 ? "yay" : "nope"; // return yay if $a == 3 or nope {% endhighlight %} Bracketing also affords us the capability of creating unions within a statement block where the block will be checked as a whole. Such as this example below which will return true if both ($a == 3 and $b == 4) are true and $c == 5 is also true. {% highlight php %} <?php return ($a == 3 && $b == 4) && $c == 5; {% endhighlight %} Another example is the snippet below which will return true if ($a != 3 AND $b != 4) OR $c == 5. {% highlight php %} <?php return ($a != 3 && $b != 4) || $c == 5; {% endhighlight %} Since PHP 5.3, it is possible to leave out the middle part of the ternary operator. Expression "expr1 ?: expr3" returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise. * [Ternary operators](https://www.php.net/language.operators.comparison)