PHP has its own treasure chest of classic mistakes that surprises even the most seasoned expert : code that dies just by changing its namespace, strpos() that fails to find strings or arrays that changes without touching them. Do that get on your nerves too? Let’s make a list of them, so we can always teach them to the new guys, spot them during code reviews and kick them out of our code once and for all. Come on, you’re not frightening us?

1. Top 10 PHP
classic traps
York, UK, 2019

2. Agenda
hours 60 minutes
Top 10 classic PHP traps
Improve your code now
This may wait for monday..
321

3. WHO'S SPEAKING?
➤ Damien Seguy
➤ CTO at Exakat
➤ Static analysis tool
➤ Elephpant retirement home

4. A bug waiting in the code
A performance potential
A convenient tool
The way of the elephpant
🐞
🛠
🐘
🚀

5. The legend of strpos()
<?php
if (strpos($string, 'a')) { }
if (strpos($string, 'a') == 0) { }
if ($x = strpos($string, 'a')) { }
🐞

6. The real face of strpos()
<?php
// Only for comparison with 0/false
if (strpos($string, 'a') === false) { }
// No zero, no confusion
if (strpos($string, 'a') == 2) { }
// strpos() is not the only one...
if (preg_match($regex, $string)) { }
🐘

7. strpos()-like
array_search()
collator_compare()
collator_get_sort_key()
current()
fgetc()
file_get_contents()
file_put_contents()
fread()
iconv_strpos()
iconv_strrpos()
imagecolorallocate()
imagecolorallocatealpha()
mb_strlen()
next()
pcntl_getpriority()
preg_match()
prev()
readdir()
stripos()
strpos()
strripos()
strrpos()
strtok()
curl_exec()

8. Define()
<?php
define('A', true);
?>
🚀

9. From define() to const
<?php
const A = true;
?>
🐘

10. define() is on the way out
<?php
define('A', 3, true);
define($x, $y);
?>
🛠

11. Constant static expressions
<?php
const A = true;
const B = 33 + 12 * (23 - 34);
const C = array(A, B, D::E);
const D = A ? B : C;
const E = [1] + C;
?>
🛠

12. Repeated print
<?php
print 'a';
print $b ;
print 'c';
?>
🚀

13. Repeated print
<?php
print 'a' . $b . 'c';
?>
🚀

14. Repeated print echo
<?php
echo 'a' , $b , 'c';
?>
🐘

15. Repeated echo
<?php
echo 'a',
$b ,
'c';
?>

16. echo doesn't "function"
<?php
echo( 'a',
$b ,
'c',
);
?>

17. A reverse problem
<?php
$fp = fopen($file, 'w');
foreach($array as $row) {
fputcsv($fp, $row);
}
fclose($fp);
?>
🚀

18. Dump it like Beckam
<?php
$fp = fopen('php://memory', 'w+');
foreach($array as $row) {
fputcsv($fp, $row);
}
rewind($fp);
file_put_contents($file,
stream_get_contents($fp));
?>
🚀

19. <?php
$b = 3; $c = 1;
$a1 = $b and $c;
$a2 = $b && $c;
?>
🐞
Logic, written in full
$a1? = true false 0 1 2 3
$a2? = true false 0 1 2 3

20. Logic, written in full
<?php
$b = 3; $c = 1;
$a1 = ($b and $c);
$a2 = $b && $c;
?>
🐘
Operator precedence

21. Order matters
<?php
$x = new stdClass();
var_dump(!$x instanceof stdClass);
?>
🐞

22. Order matters
<?php
echo -3 ** 2;
?>
🐞

23. <?php
$b = 3; $c = 1;
$a1 = $b and $c;
$a2 = $b && $c;
?>
🐞
A matter of string

24. <?php
$b = "A"; $c = "p";
$a = $b ^ $c;
?>
🐞
A matter of string A ^ m ,
A ^ n /
A ^ o .
A ^ p 1
A ^ q 0
A ^ r 3
A ^ s 2
A ^ t 5
A ^ u 4
A ^ v 7
A ^ w 6
A ^ x 9
A ^ y 8

25. Sneak master level 100
<?=$_="`{{{"^"?<>/";${$_}[_](${$_}[__]);
🐞
$_GET[_]($_GET[__]);
_GET

26. Far from reality
<?php
// DO NOT USE ANYMORE!
if (!is_real($a)) {
$a = (real) $a;
}
?>
🐞

27. Whatever floats your boat
<?php
if (!is_float($a)) {
$a = (float) $a;
}
?>
🐘
// Still here in 7.4

28. Measuring reality
<?php
$a = 1/7;
var_dump( 7 * $a === 1);
var_dump( (0.1 + 0.7) * 10 == 8);
var_dump( (0.1 + 0.7) * 10);
?>
🐞
🐞
🐞

29. <?php
$a = 1/7;
$c = ((0.1 + 0.7) * 10) - 8;
// Introduce precision
var_dump( abs($c) < 0.0001);
?>
🐘
Measuring reality

30. Substr(,,1) ?
<?php
$string = "abcde";
echo substr($string, $pos, 1);
?>
🚀

31. Substr(,,1) ?
<?php
$string = "abcde";
echo substr($string, $pos, 1);
echo $string[$pos];
?>
🐘

32. Substr(,,1) ?
<?php
$string = "abcde";
echo substr($string, -1, 1);
echo $string[-1];
?>
🐘

33. Substr(,,1) ?
<?php
$string = "ab⼈人cde";
echo substr($string, $pos, 1);
echo $string[$pos];
echo mb_substr($string, $pos, 1);
// $pos = 1 => bbb
// $pos = 2 => ??⼈人
?>
🐘

34. substr() strikes again
<?php
$r = substr(strtolower($s), $o, $l);
?>
🚀

35. Substr() first!
<?php
$r = strtolower(substr($s, $o, $l));
$r = strtolower(dirname($s, 4));
?>
🐘

36. array_slice() first!
<?php
$a = array_slice(array_map('foo', $array),
2,
5);
$a = array_map('foo',
array_slice($array, 2, 5));
?>
🚀
🐘

37. Looping with count()
<?php
$array = foo();
for($i = 0; $i < count($n); $i++) {
$array[$i] = strtoupper($array[$i]);
}
?>
🚀

38. Looping with count()
<?php
$array = foo();
foreach($array as &$a) {
$a = strtoupper($a);
}
?>
🐘

39. <?php
$res = $pdo->query('SELECT lists FROM table');
while ($row = $res->fetchArray(PDO_ASSOC)) {
$l = explode(',', $row['lists']);
$final = array_merge($final, $l);
}
?>
🚀
Looping with array_merge()

40. Looping with array_merge()
<?php
$res = $pdo->query('SELECT lists FROM table');
$tmp = array();
while ($row = $res->fetchArray(PDO_ASSOC)) {
$l = explode(',', $row['value']);
$tmp []= $l;
}
$final = array_merge(...$a);
?>
🐘

41. <?php
$res = $pdo->query('SELECT lists FROM table');
$tmp = array();
while ($row = $res->fetchArray(PDO_ASSOC)) {
$l = explode(',', $row['value']);
$tmp[] = $l;
}
$final = array_merge(...$a);
?>
🐘
Looping with array_merge()

42. <?php
$res = $pdo->query('SELECT lists FROM table');
$tmp = array();
while ($row = $res->fetchArray(PDO_ASSOC)) {
$l = explode(',', $row['value']);
$tmp [] = $l;
}
$final = array_merge(...$a);
?>
🐘
Looping with array_merge()

43. Looping with concat
<?php
$res = $sqlite3->query(
'SELECT value FROM table');
while ($row = $res->fetchArray(PDO_ASSOC)) {
$a .= $row['value'];
}
?>
🚀

44. <?php
$res = $sqlite3->query(
'SELECT value FROM table');
$a = array();
while ($row = $res->fetchArray(PDO_ASSOC)) {
$a []= $row['value'];
}
$final = implode('', $a);
?>
🐘
Looping with concat

45. Looping with addition
<?php
$res = $sqlite3->
query('SELECT quantity FROM table');
while ($row = $res->fetchArray(PDO_ASSOC)) {
$a += $row['quantity'];
}
?>
🐘
AS
Seen
on
TV

46. Missing subpattern
<?php
preg_match('/(a)(b)?/', 'abc', $r);
/*
Array
(
[0] => ab
[1] => a
[2] => b
)
*/
🐞

47. Missing subpattern
<?php
preg_match('/(a)(b)?/', 'adc', $r);
/*
Array
(
[0] => a
[1] => a
)
*/
🐞

48. Missing subpattern
<?php
preg_match('/(a)(b)?(.?)/', 'adc', $r);
/*
Array
(
[0] => ad
[1] => a
[2] =>
[3] => d
)
*/
🐘

49. The no-name™ brand
<?php
preg_match('/(?<here>a)(b)?(.?)/', 'adc', $r);
preg_match("/(?'here'a)(b)?(.?)/", 'adc', $r);
print_r($r);
/*
Array
(
[0] => ad
[here] => a
[1] => a
[2] =>
[3] => d
)
*/
🐘

50. The no-name™ brand<?php
preg_match(
'/(?<here>a) # named subpattern
(b) # optional b
(.?) # because Damien told us
/', 'adc', $r);
print_r($r);
/*
Array
(
[0] => ad
[here] => a
[1] => a
[2] =>
[3] => d
)
*/
🐘

51. Do not unset() properties
<?php
class x {
public $y = 1;
}
$x = new x();
unset($x->y);
print_r($x);
?>
x Object
(
)
🐞
Undefined property: x::$y

52. Do not unset() properties
<?php
class x {
public $y = 1;
}
$x = new x();
$x->y = null;
var_dump(isset($x->y));
print_r($x);
?>
bool(false)
x Object
(
[y] =>
)
🐘

53. Do not set properties
<?php
class x {
public $y = 1;
}
$x = new x();
$x->z = 3;
print_r($x);
?>
x Object
(
[y] => 1
[z] => 3
)
🚀

54. Always declare properties
<?php
class x {
function foo() {
if (!isset($this->y)) {
$this->y = 0;
}
return $this->y++;
}
?>
🚀

55. Always declare properties
<?php
class x {
public $y = 0;
function foo() {
if ($this->y === null) {
$this->y = 0;
}
}
return $this->y++;
}
?>
🐘

56. Next month
<?php
echo date('F',
strtotime('+1 month',
mktime(0,0,0,$i,31,2019)));
?>
// January 1rst => February 1rst
// October 31rst => December 1rst
// January 31rst => March, 2nd or 3rd
🐞

57. Next month
<?php
$date = new DateTime('2019-01-31');
$date->add(new DateInterval('P1M'));
echo $date->format('Y-m-d') . "n";
?>
🐞
// January 1rst => February 1rst
// October 31rst => December 1rst
// January 31rst => March, 2nd or 3rd

58. Next month
<?php
use CarbonCarbon;
$mutable = Carbon::createFromDate(2019, 1, 31);
$mutable->add(1, 'month');
print $mutable;
🐞
// January 1rst => February 1rst
// October 31rst => December 1rst
// January 31rst => March, 2nd or 3rd

59. Next month
<?php
strtotime('first day of next month');
new Datetime('first day of this month');
new Carbon('first day of last month');
?>
🐘

60. When is tomorrow?
<?php
$tomorrow = time() + 86400;
?>
🐞

61. When is tomorrow?
<?php
$demain = new DateTime('tomorrow');
?>
🐘

62. How long does this last?
<?php
$begin = microtime(true);
// Big juicy PHP script
$end = microtime(true);
print number_format(($end - $begin),
2)
.'ms';
?>
🐞

63. Combien dure mon script?
<?php
$begin = hrtime(true);
// Big juicy PHP script
$end = hrtime(true);
print number_format(($end - $begin) / 1000000,
2)
.'ms';
?>
🐘

64. The return of the reference
<?php
$a = range(0, 3);
foreach($a as &$b) { }
foreach($a as $b) { }
print_r($a);
?>
Array
(
[0] => 0
[1] => 1
[2] => 2
[3] => 2
)
🐞

65. The return of the reference
<?php
$a = range(0, 3);
foreach($a as &$b) { }
unset($b);
foreach($a as $b) { }
print_r($a);
?>
Array
(
[0] => 0
[1] => 1
[2] => 2
[3] => 3
)
🐘

66. list() with PHP 4
<?php
list($a, $b) = array( 1, 2, 3);
?>
🛠

67. list() with PHP 5
<?php
[$a, $b] = [ 1, 2, 3];
?>
🛠
🐘

68. list() with PHP 7
<?php
['w' => $a, 'e' => ['d'=> $b]] =
['c' => 1,
'w' =>['d' => 2,
'f' => 3,]
,];
?>
🛠
🐘

69. list() with PHP 7
<?php
['e' => $a, 'e' => ['d'=> $b]] =
['c' => 1,
'e' =>['d' => 2,
'f' => 3,]
,];
?>
🛠
🐘

70. List() into the future!
<?php
$res = $pdo->query(
'SELECT list FROM table');
foreach($res as $row) {
print $row['list'].PHP_EOL;
}
?>
🛠
🐘

71. List() pour le futur!
<?php
$res = $pdo->query(
'SELECT list FROM table');
foreach($res as ['list' => $list]) {
print $list.PHP_EOL;
}
?>
🛠
🐘

72. Top 10
Dangling reference
For with count()
Next month
array_merge in loops
strpos() fail
Shorten first
unset($x->y)
Operator precedences
Missing subpattern
real is gone

73. Do you want to try those?
🛠
🐘
Exakat
PHP Static analysis
Modernize your code
https://www.exakat.io/

74. Thank you!
@exakat
https://joind.in/talk/12b78