I’ve mentioned quite a few times that I am a big fan of Perl programming languge.\u00a0 However, most of my programming time these days is spent in PHP.\u00a0 The languages are often similar, with PHP having its roots in Perl, and Perl being such a influence in the world of programming languages.\u00a0 This similarity is often very helpful.\u00a0 However there are a few difference, some of which are obvious and others are not.<\/p>\n
One such difference that I came up recently (in someone else’s code though), was about variable scoping.\u00a0 Consider an example in Perl:<\/p>\n
#!\/usr\/bin\/perl -w\r\nuse strict;\r\nmy @values = qw(foo bar hello world);\r\nforeach my $value (@values) {\r\n\u00a0\u00a0\u00a0 print \"Inside loop value = $value\\n\";\r\n}\r\nprint \"Outside loop value = $value\\n\";<\/pre>\nThe above script will generate a compilation error due to undefined variable $value.\u00a0 The one outside the loop.<\/p>\n
A very similar code in PHP though:<\/p>\n
#!\/usr\/bin\/php\r\n<?php\r\n$values = array('foo','bar','hello','world');\r\nforeach ($values as $value) {\r\n\u00a0\u00a0\u00a0 print \"Inside loop value = $value\\n\";\r\n}\r\nprint \"Outside loop value = $value\\n\";\r\n?><\/pre>\nWill output the following:<\/p>\n
Inside loop value = foo\r\nInside loop value = bar\r\nInside loop value = hello\r\nInside loop value = world\r\nOutside loop value = world<\/pre>\nIn Perl, variable $value is scoped inside the loop.\u00a0 Once the execution is out of the loop, there is no such thing as $value anymore, hence the compilation error (due to the use of strict and warnings).\u00a0 In PHP, $value is in global scope, so the last value “world” is carried further down the road.\u00a0 In case you reuse variable names in different places of your program, counting on scope to be different, you might get some really interesting and totally unexpected results.\u00a0 And they won’t be too easy to track down too.\u00a0 Be warned.<\/p>\n\n","protected":false},"excerpt":{"rendered":"\n