$re = '/IF NOT EXISTS \(SELECT \* FROM sys\.objects WHERE object_id = OBJECT_ID\(N\'\[(.*?)\]\.\[(.*?)\]\'\) AND type = \'D\'\)
BEGIN
ALTER TABLE \[(.*?)\]\.\[(.*?)\] ADD DEFAULT \(\((.*?)\)\) FOR \[(.*?)\]/m';
$str = 'GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF_EnrollmentPeriod_MedPlans_IsActive]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[EnrollmentPeriod_MedPlans] ADD CONSTRAINT [DF_EnrollmentPeriod_MedPlans_IsActive] DEFAULT ((0)) FOR [IsActive]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__12:00__3EFC4F81]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [12:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__1:00 __3FF073BA]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [1:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__2:00 __40E497F3]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [2:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__3:00 __41D8BC2C]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [3:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__4:00 __42CCE065]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [4:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__5:00 __43C1049E]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [5:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__6:00 __44B528D7]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [6:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__7:00 __45A94D10]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [7:00 AM]
END
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N\'[dbo].[DF__HourlyUsa__8:00 __469D7149]\') AND type = \'D\')
BEGIN
ALTER TABLE [dbo].[HourlyUsageHistory] ADD DEFAULT ((0)) FOR [8:00 AM]
END
';
$subst = "IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[\1].[\2]') AND type = 'D')BEGINALTER TABLE [\3].[\4] ADD CONSTRAINT [\2] DEFAULT ((\5)) FOR [\6]";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php